US20060287745A1 - Wireless speakers - Google Patents

Abstract

A wireless audio distribution system may include a wireless transmitter, responsive to a plurality of audio input channels, for transmitting an encoded digital bitstream serially combining each of the audio input channels with control data a receiver responsive to the transmitted encoded digital bitstream for decoding a preselected one of the plurality of the audio input channels from the digital bitstream for reproduction and at least one speaker for reproducing the preselected audio input channel in accordance with the control data. A wireless speaker system may include a receiver, responsive to a wirelessly transmitted, encoded digital bitstream serially combining each of a plurality of the audio input channels with control data disbursed therein, for decoding a preselected one of said audio input channels and a speaker system responsive to the receiver for reproducing the decoded, preselected audio input channel.

Description

RELATED APPLICATIONS
• This Application is a Division of application Ser. No. 11/282,974 filed Ser. No. 11/18/2005 which is a Continuation of application Ser. No. 10/691,899 filed on 10/22/03—which claims the priority of Provisional Application No. 60/420,375 filed on 10/22/02 and International Application No. PCT/U03/00566 filed on 1/8/03—which is a Continuation-in-Part of application Ser. No. 10/189,091 filed on 7/3/02 which claims priority of Provisional Application No. 60/340,744 filed on 10/30/01, Provisional Application No. 60/347,073 filed on 1/8/02 and Provisional Application No. 60/350,646 filed on 1/22/02; all of which are hereby incorporated by reference as if set forth fully herein.
BACKGROUND OF THE INVENTION
• This invention relates to wireless communication systems, and more particularly to wireless audio and video systems for providing a plurality of selectable audio-video signals from one or more sources to one or more listeners in an automobile, airplane, or building.
• Wireless audio systems currently known and available generally include an audio source such as a tuner transmitting a signal to one or more wireless headphones, wherein the signal carries a single stereo channel of audio data. To select a different channel of audio data, someone must operate the tuner to transmit the newly desired channel, at which point all wireless headphones receiving the signal will begin reproducing the new channel.
• Dual-channel systems are currently known. For instance, the Two-Channel Automotive Infrared Headphone System marketed by Unwired Technology LLC provides an infrared transmitter that may be connected to two stereo sources and that will transmit a different IR signal for each channel. Wireless headphones are provided with a channel A/B selector switch to allow the user of the headphone to select among the two channels. This system requires two separate stereo sources, and relies on IR LEDs of different frequencies (i.e. color) the differentiate between the two channels of audio. This system also requires installation of the transmitter at a location where the two signals being broadcast may be received at any location within the vehicle.
• Wireless video systems are also known.
• What is needed is an improved wireless communication system including one or more wireless reception devices such as headphones, wherein the system offers multiple channels of audio and video signals, and other data, for individual selection therebetween by each respective reception device. The system should occupy a minimum of space within the home or vehicle, and should ideally be flexible enough to allow both analog and digital communications and minimize interference between different signals transmitted concurrently.
SUMMARY OF THE INVENTION
• A wireless audio distribution system may include a wireless transmitter, responsive to a plurality of audio input channels, for transmitting an encoded digital bitstream serially combining each of the audio input channels with control data, a receiver responsive to the transmitted encoded digital bitstream for decoding a preselected one of the plurality of the audio input channels from the digital bitstream for reproduction and at least one speaker for reproducing the preselected audio input channel in accordance with the control data. A selector for selecting the preselected audio channel for reproduction by the at least one speaker may be used. A control unit responsive to at least portions of the control data may be used for controlling the reproduction of the preselected audio channel by the speaker in accordance with the at least portions of the control data. The control unit may decode the preselected audio input channel from the digital bitstream in accordance with the at least portions of the control data. An input device may be provided for inputting the selection of one of the plurality of audio input channels to be the preselected audio channel and the wireless transmitter, the receiver and/or the digital bitstream may be responsive to the selection of the preselected channel.
• Additional receivers and/or speakers may be used for decoding and reproducing a second preselected audio input channel from the digital bitstream. Pairs of additional receivers and speakers may be used to reproduce audio channels representing music as heard by a listener from different directions including from the front and rear of the listener. A pair of wireless headphone responsive for reproducing the preselected audio channel in accordance with the control data may also be used together a selector switch for selecting either the speaker or the headphones to reproduce the preselected audio input channel. The selector switch may cause a modification of the control data to selectively cause the speaker or the headphones to reproduce the preselected audio input channel. An error detection circuit for comparing portions of the control data to detect errors may be used together with an off circuit for turning off the selected speaker or headphone if the detected errors exceed a predetermined threshold. An error correction circuit may also be provided for correcting the detected errors.
• Additional receivers and/or speakers may be used for decoding and reproducing a second preselected audio input channel from the digital bitstream. Pairs of additional receivers and speakers may be used to reproduce audio channels representing music as heard by a listener from different directions including from the front and rear of the listener. A pair of wireless headphone responsive for reproducing the preselected audio channel in accordance with the control data may also be used together a selector switch for selecting either the speaker or the headphones to reproduce the preselected audio input channel. The selector switch may cause a modification of the control data to selectively cause the speaker or the headphones to reproduce the preselected audio input channel. An error detection circuit for comparing portions of the control data to detect errors may be used together with an off circuit for turning off the selected speaker or headphone if the detected errors exceed a predetermined threshold. An error correction circuit may also be provided for correcting the detected errors.
• A wireless speaker system may include a receiver, responsive to a wirelessly transmitted, encoded digital bitstream serially combining each of a plurality of the audio input channels with control data disbursed therein, for decoding a preselected one of said audio input channels and a speaker system responsive to the receiver for reproducing the decoded, preselected audio input channel. A control unit responsive to at least portions of the control data may be used for controlling the reproduction of the preselected audio channel by the speaker in accordance with the control data and the preselected audio input channel may be selected by the control data, the receiver and/or the speaker
• These and other features and advantages will become further apparent from the detailed description and accompanying figures that follow. In the figures and description, numerals indicate the various features, like numerals referring to like features throughout both the drawings and the description.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a block diagram of wireless headphone system.
• FIG. 2 is a block diagram ofwireless headphone system10 using an analog signal combining configuration.
• FIG. 3 is a block diagram of one embodiment of a data stream format used in a wireless headphone system, such aswireless headphone system10 depicted inFIGS. 1 and 2.
• FIG. 4 is a block diagram schematic of one embodiment of a receiver or headset unit, such asheadset receiver unit14 depicted inFIG. 1.
• FIG. 5 includes top and front views of one embodiment of multi-channel headphones for use insystem10.
• FIG. 6 depicts a functional block diagram oftransmitter apparatus500.
• FIG. 7 depicts a hardware block diagram ofencoder626 oftransmitter apparatus500 ofFIG. 6.
• FIG. 8 is a functional block diagram of clock andclock phasing circuitry628 oftransmitter apparatus500.
• FIG. 9 is a functional block diagram of inputaudio conversion module622 oftransmitter apparatus500.
• FIG. 10 is a functional block diagram ofIR module emitter634 oftransmitter apparatus500.
• FIG. 11 depicts a configuration of transmission data input buffers for use withtransmitter apparatus500.
• FIG. 12 depicts a digital data transmission scheme, that may be used withtransmitter apparatus500.
• FIG. 13 depicts a functional block diagram of receiver apparatus orheadset unit700, that may be used in conjunction with a transmitter apparatus such astransmitter apparatus500.
• FIG. 14 is a functional block diagram ofprimary receiver702 ofreceiver apparatus700.
• FIG. 15 is a functional block diagram ofIR receiver714 ofreceiver apparatus700.
• FIG. 16 is a functional block diagram of dataclock recovery circuit716 ofreceiver apparatus700.
• FIG. 17 is a functional block diagram of DAC andaudio amplifier module722 ofreceiver apparatus700.
• FIG. 18 is a functional block diagram ofsecondary receiver704 ofreceiver apparatus700.
• FIG. 19 is a diagram of avehicle800 equipped withcommunication system801.
• FIG. 20 is a diagram of anothervehicle800 equipped withcommunication system801 having additional features over that shown inFIG. 19.
• FIG. 21 is a diagram ofvehicle900 equipped withcommunication system901.
• FIG. 22 is a diagram of avehicle988 equipped with awireless communication system991; and
• FIG. 23 is a diagram of abuilding1010 equipped with awireless communication system1000.
• FIG. 24 is a schematic diagram of an alternate configuration in which separate wireless receiver/transmitters separately communicate with separate headset receivers which may include transmitters.
• FIG. 25 is a schematic diagram of a further embodiment in which one or more wireless receiver/transmitters may be positioned behind a vehicle headliner transparent to the radiation used in the wireless system.
• FIG. 26 is a diagram of a wireless computer speaker or headphone system.
• FIG. 27 is a diagram of a wireless audio distribution system including a portable audio source.
DETAILED DESCRIPTION OF THE INVENTION
• Referring toFIG. 1, one embodiment of a wireless communication system disclosed iswireless headphone system10 that includestransmitter subsystem12 that communicates withheadset unit14 via infra-red (IR) or radio frequency (RF) signals16, preferably a formatted digital bit stream including multi-channel digitized audio data, calibration data as well as code or control data. The data being transmitted and received may comply with, or be compatible with, an industry standard for IR data communications such as the Infra Red Data Association or IRDA.
• Transmitter subsystem12 may includeIR transmitter section18 includingIR transmitter20, such as an infra-red light emitting diode or LED, driven by an appropriateIR transmitter driver22 receiving digitized audio data from one or more digital signal processors, or DSPs, such as DSP encoder andcontroller24,27,28 and/or30. The digital data stream provided byIR transmitter section18 is preferably formatted in accordance with any one of the proprietary formats described herein below with reference toFIGS. 3, 10 and16.
• The digitized audio data may be applied toIR transmitter driver22 from a plurality of such DSP encoder and controllers that are combined in signal combiner/multiplexer32 that may be separately provided, combined withIR transmitter section18 or combined with DSP encoder andcontroller24 inmaster controller26.Master controller26 may be included within a first audio device, such asaudio device34 as shown, provided as a separate unit or included withinIR transmitter section18.
• In a system configuration in whichmaster controller26 is included withinaudio device34,wireless headphone system10 includingaudio device34,IR transmitter section18 andheadset unit14 may advantageously serve as a base or entry level system suitable for use as a single channel wireless headphone system that, in accordance with the proprietary formats described herein below with regard toFIGS. 3, 10 and16 may be easily upgraded for use as a multi-channel wireless headphone system. For illustrative purposes,audio device34 is depicted inFIG. 1 as includingaudio stage36, having first and second audio sources such asline1source38 andline2source40 each connected to stereo processing circuitry such asstereo channel1circuitry42, the output of which is applied tomaster controller26.Audio device34 thereby represents any audio, video or data source including mono and stereo radios, CD and cassette players, mini-disc players, as well as the audio portions of electronic devices that provide other types of signals such as computers, television sets, DVD players and the like.
• Whether included as part of an initial installation, or later upgraded, a second audio source, such as MP3, WMA, or other digitalaudio format player44, may be included withinwireless headphone system10 to provide a second channel of stereo audio signals. In particular,MP3 player44 may conveniently be represented byaudio stage46 that providesline3 source48 andline4 source50 tostereo channel circuitry52, the output of which may be a line out, speaker out or headphone out port. As shown inFIG. 1, the output ofstereo channel circuitry52 may be applied to DSP encoder andcontroller27 for combining in signal combiner/multiplexer32 ofmaster controller26 included withinaudio device34. In this manner, an unmodified conventional stereo audio source such asMP3 player44 may be added towireless headphone system10 by use of an add on DSP device such as DSP encoder andcontroller27.
• Alternately, a DSP device included within an audio source for other purposes, such as related to the production of a digitized audio signal, may be programmed to provide the control and formatting required for providing an additional channel of data forwireless headphone system10. In particular, new unit add indevice54 is shown as an exemplar of an audio source in which an included DSP has been programmed for compatibility with the proprietary format described herein below with regard toFIG. 3.Device54 generally includesline5source56 as well asline6source58, both connected throughstereo channel circuitry60 to DSP encoder andcontroller28 for application to signal combiner/multiplexer32.
• Similarly, an analog audio device may be included inwireless headphone system10 by use of a legacy adapter, such aslegacy adapter62.Legacy adapter62 is illustrated as includingline7analog audio input64 andline8analog audio input66 both connected tostereo channel circuitry68 for application to DSP encoder andcontroller30. It should be noted that any one of the audio inputs designated aslines1 through8, may be paired as stereo input lines, used singly as separate monaural inputs, or in any other convenient combinations of stereo and mono inputs or as part of a more complex audio format, such as a home theater 5.1 or 7.1 system. Any one or more oflines1 through8 may also be used to transmit non-audio data, as described in more detail elsewhere herein.
• As depicted inFIG. 1,wireless headphone system10 may include one or more digital audio sources and may also include one or more analog audio sources. As shown,transmitter subsystem12 may include a single digital signal combiner, such as signal combiner/multiplexer32, fed by digital signals from each of a plurality of DSPs, such as DSP encoder andcontrollers24,27,28 and30. An alternate configuration oftransmitter subsystem12 using analog signal inputs will be described below in greater detail with respect toFIG. 2.
• Still referring toFIG. 1,IR transmitter20 inIR transmitter section18 produces a digital bit stream of IR data, designated as IR signals16, from a convenient location having a direct line of sight path toIR receiver70 inheadset receiver unit14. In a home theater application,IR transmitter20 might conveniently be located at the top of a TV cabinet having a clear view of the room in which the listener will be located. In a vehicular application,IR transmitter20 could be located in a dome light in the center of the passenger compartment, or may be a separate component mounted at a desirable and practicable location (such as near the dome light). In a larger area in which multipleheadset receiver units14 are to be driven by thesame IR transmitter20,IR transmitter section18 may include a plurality ofIR transmitters20 each conveniently located to have a direct line of sight path to one or moreheadset receiver units14. In other embodiments, as described elsewhere with regard toFIG. 17, IR transmission repeaters may be provided to relay the digital bit stream transmitted by asingle transmitter20 over longer distances or around obstacles that may otherwise block the direct line(s) of sight fromtransmitter20 to any one or more ofheadset receiver units14.
• In many applications, the output ofIR receiver70 may conveniently be processed by IR receivedsignal processor72. In either event, after being received, IR signals16 are then applied todecoder74, containing a clock, de-multiplexer, and controller, for processing to provide separate digital signals for stereo channels1-4 to be applied toDSP76 for processing.DSP76 may conveniently be a multiplexed DSP so that only a single DSP unit is required. Alternately, a plurality of DSP units or sub units may be provided.
• The stereo audio channels1-4 may conveniently each be processed as individual left and right channels, resulting in channels1L,2R,2L,2R,3L,3R,4L and4R as shown. It should be noted, as discussed above that each of these audio channels may be used as a single monaural audio, or data channel, or combined as shown herein to form a sub-plurality of stereo channels. The resultant audio channels are then made available to switchingselector78 for selective application to wireless headphone headset earphones, generally designated asheadphones80.
• In general, switchingselector78 may be conveniently used by the listener to select one of stereo channels1-4 to be applied toheadphones80. Alternately, one or more of the stereo channels can be used to provide one or two monaural channels that may be selected by the listener, or in specific circumstances automatically selected upon the occurrence of a particular event. In theevent headphones80 are equipped to receive four (or any other number of) stereo audio channels, but a lesser number of channels are available for transmission byaudio device34, the number of actual channels being transmitted may be incorporated into the digital bit stream ofsignals16, and the headphones may then allow a user to select only those channels that are available (e.g. if only two channels are being transmitted, the user would only be able to toggle between these two channels, without having to pass through two or more “dead” channels).
• For example, switchingselector78 may be configured to permit the listener to select one of three stereo channels, such as channels1-3, while stereo channel4L may be used to provide a monaural telephone channel and channel4R may be used to provide an audio signal such as a front door monitor or a baby monitor. In the case of a baby monitor, for example, switchingselector78 may be configured to automatically override the listener's selection of one of the stereo channels to select the baby monitor audio whenever the audio level in the baby monitor channel exceeds a preset level. Further, a fixed or adjustable time period after the audio level in the baby monitor channel no longer exceeds the preset level, switchingselector78 may be configured to automatically return to the stereo channel earlier selected by the listener.
• Alternately, stereo channels1-3 may be utilized to provide an audio format, such as the 5.1 format used for home and professional theaters. In this type of format, a first stereo channel is used to provide a front stereo sound source located left and right of the video being displayed. Similarly, a second stereo channel may be used to provide a rear stereo sound source located left and right behind the listener. A so-called fifth channel may be a monaural channel providing a non-stereo sound source located at a center position between the left and right front stereo sources. A further monaural channel, representing the so-called “0.1” channel, may conveniently be a low frequency woofer or subwoofer channel whose actual location may not be very critical as a result of the lower audio frequencies being presented. Similarly, stereo channels1-4 may be utilized to provide audio in the so-called 7.1 audio format.
• Headphones80 may conveniently be a pair of headphones speakers mounted for convenient positioning adjacent the listener's ears, particularly for use withwireless headphone system10 configured for permitting user or automatic or override selection of a plurality of stereo or monaural channels.Headphones80 may be used in this configuration to present audio to the listener in a format, such as the 5.1 format, by synthesis. For example, the center channel of the 5.1 format may be synthesized by combining portions of the front left and right channels.
• Alternately, as described below with respect toFIG. 5, alternate configurations ofheadphones80 may be used to provide a more desirable rendition of a particular format by providing a plurality of pairs of headphone speakers mounted in appropriate positions adjacent the listener's ears. For example, a first pair of speakers may be positioned in a forward position to reproduce the front left and right channels and to synthesize the center channel, a second pair of speakers may be positioned in a rearward position to reproduce the rear left and right channels, with a resonant chamber mounted to a headband supporting the speakers is used to provide the subwoofer (0.1) channel.
• Referring now again toFIG. 1,decoder74 may also be used to produce control signals used for providing additional functions. For example, control signals may be incorporated into the digital bit stream transmitted byaudio device34 for error checking, power saving, automatic channel selection, and other features as described elsewhere herein. In addition to audio signals provided toDSP76,decoder74 may also be used to providepower control signal82 for application tobattery system84. In particular, in response to the decoding of a code contained in the proprietary formats discussed elsewhere,decoder74 may provide a signal, such aspower control signal82, maintaining the application of battery power frombattery system84 towireless headphone system10. Thereafter, when the coded signal has not been received for an appropriate time period, battery power would cease to be applied tosystem10 to provide an automatic auto-off feature that turns offsystem10 to preserve battery power when the sources of audio signals, or at least the formatted signals, are no longer present. This feature can conveniently be used in an application in whichsystem10 is used in a car. When the ignition of the car has been turned off, the power applied toheadset receiver unit14 frombattery system84 is stopped in order to preserve battery life. As discussed elsewhere, the automatic auto-off feature may also be invoked when an error checking feature detects a predetermined number of errors.
• Referring now toFIG. 2, in an alternative embodiment,transmitter subsystem13 may be configured with a single DSP, for digitizing audio signals, that is programmed to provide signal combining and format control functions. In particular, the input toIR transmitter section18 may be provided directly by a properly configured DSP encoder andcontroller24 that receives as its inputs, the analog audio signal pairs fromstereo channels1,2,3 and4 provided by stereo integrated circuits, or ICs,42,52,60 and68, respectively. As alternatives to the use of a DSP, any practicable means for performing the functions herein described, including any other electronic circuit such as a gate array or an ASIC (Application Specific Integrated Circuit) also may be employed. For ease of understanding, however, the term DSP is used throughout this specification.
• The source of stereo inputs forstereo channel circuitry42 inaudio stage36 may conveniently beline1source38 andaudio stage36. The source of stereo input forstereo channel circuitry52 inMP3 player44 may beline3 source48 andline4 source50, provided byaudio stage46. Similarly, the sources of stereo input forstereo channel circuitry60 and68 in new unit add indevice54 andlegacy adapter62 may beline5source56 andline6source58 as well asline7analog audio input64 andline8analog audio input66, respectively. It is important to note that all four stereo sources may be combined to provide the required audio signals for a complex format, such as 5.1, or one or more of such stereo channels can be used as multiple audio channels.
• Referring now toFIG. 3, the format or structure of IR signals16 is shown in greater detail. IR signals16 form a bit stream of digital data containing the digitized audio data for four stereo channels, as well as various calibration and control data. In one embodiment, IR signals16 are an uncompressed stream of digital data at a frequency or rate of at least 10.4 MHz. Pulse position modulation (PPM) encoding is preferably used. This encoding increases the power level of pulses actually transmitted, without substantially increasing the average power level of the signals being transmitted, by using the position of the pulse in time or sequence to convey information or data. This power saving occurs because in PPM encoding, the same amount of information carried in a pair of bits at a first power level in an unencoded digital bitstream may be conveyed by a single bit used in one of four possible bit positions (in the case of four pulse position modulation, or PPM-4, encoding). In this way, the power level in the single bit transmitted in pulse position encoding can be twice the level of each of the pair of bits in the unencoded bitstream while the average power level remains the same.
• As shown inFIG. 3, IR signals16 include a plurality of transmitted signals (or packets, as described elsewhere herein)86 separated from each other bygap100 that may conveniently simply be a 16 bit word formed of all zeros.Gap100 is useful to convey clocking information for synchronizing the receiver decoding to the clock rate of the transmitter, as described below in greater detail with respect toFIG. 4.
• Transmitted signals orpackets86 may conveniently be partitioned into two sections,header section87 anddata section88, as shown.Data section88 may conveniently be composed of25 samples of each of the 8 audio data streams included in the four stereo signals being processed. For example,data section88 may includeword103 representing the sampled digital output orstereo channel1, left whileword104 represents the sampled digital output ofstereo channel1, right, followed by representations of the remaining 3 stereo channels. This first described group of 8 digital words represents a single sample and is followed by another 24 sets of sequential samples of all 8 audio signals. In this example, eachdata section88 includes 400 digital words to provide the 25 samples of audio data. If the data rate of the analog to digital, or A/D, conversion function included within DSP encoder andcontroller24 shown inFIG. 1 is 16 bits, the first 8 bit word for each channel could therefore represent the high bit portion of each sample while the second 8 bit word could represent the low bit portion of the sample.
• Referring now also toFIG. 1, if switchingselector78 is operated to select a particular monaural or stereo channel, such aschannel3, left, the known order of the samples may be utilized to reduce the energy budget ofheadset receiver unit14. In particular, digital to analog (D/A) conversions may be performed during eachdata section88 only at the time required for the selected audio or stereo channels such aschannel3, left. In this manner, because the D/A conversions are not being performed for all 8 monaural or 4 stereo channels, the power consumed by the D/A conversions (that are typically a substantial portion of the energy or battery system budget) may be substantially reduced, thereby extending battery and/or battery charge, life.
• The organization of data block92 described herein may easily be varied in accordance with other known data transmission techniques, such as interleaving or block transmission. Referring specifically toFIG. 3, in one embodiment each transmittedpacket86 may includeheader section87 positioned beforedata section88. Eachheader section87 may include one ormore calibration sections101 andcontrol code sections102. In general,calibration sections101 may provide timing data, signal magnitude data, volume and/or frequency data as well as control data related, for example, to audio format or other acoustic information.Control code sections102 may include information used for error detection and/or correction, automatic channel selection, automatic power-off, and other features ofsystem10. Another preferred embodiment is described elsewhere herein with reference toFIG. 12.
• In particular installations, desired acoustic characteristics or the actual acoustic characteristics of the installed location oftransmitter subsystem12 may be synthesized or taken into account for the listener. For example, the relative positions including azimuth and distance of the various sound sources or speakers to the listener, in a particular concert hall or other location, may be represented in the calibration data so that an appropriate acoustic experience related to that concert hall may be synthesized for the listener usingheadset receiver unit14 by adjusting the relative delays between the channels. Such techniques are similar to those used to establish particular audio formats such as the 5.1 format.
• Alternately, undesirable acoustic characteristics, such as the high pitched whine of an engine, the low pitched rumble of the road or airplane noise, that may penetrate the acoustic barrier ofheadphones80 may be reduced or eliminated by proper use of the calibration data. This synthesis or sound modification may be controlled or aided by information in calibration portions or IR signals16, such ascalibration sections101, and/or controlled or adjusted by the listener by proper operation of switchingselector78, shown inFIG. 1.
• Similarly, the acoustic experiences of different types or styles ofheadphones80 may be enhanced or compensated for. Conventional headphone units typically include a pair of individual speakers, such as left andright ear speakers81 and83 as shown inFIG. 1. A more complex version ofheadphones80, such as multi-channel headphones118 described below in greater detail with respect toFIG. 5, may benefit from calibration data included incalibration sections98.
• Techniques for adjusting the listener's acoustic experience may be aided by data withincalibration sections101, and/or by operation of switchingselector78, as noted above, and also be controlled, adjusted or affected by the data contained incontrol code section102.Control code data102 may also be used for controlling other operations ofsystem10, such as an auto-off function ofbattery system84, error detection and/or correction, power saving, and automatic available channel selection.
• Referring now toFIGS. 4, 5 and1, IR data in processedIR packets86, such asdata section88, may conveniently be applied toDSP76, viadecoder74, for conversion to analog audio data. IR data inheader section87 may be further processed by other circuits, conveniently included within or associated withdecoder74, for various purposes.
• For use in an auto-off function, the portion of the IR data processed by IR receivedsignal processor72 includingcontrol code section102 may be applied tocode detector106 to detect the existence of a predetermined code or other unique identifier. Upon detection of the appropriate code, delay counter108 may be set to a predetermined delay, such as 30 seconds. Upon receipt of another detection of the selected code, delay counter108 may then be reset to the predetermined delay. Upon expiration of the predetermined delay, that is, upon expiration of the predetermined delay with recognition of the pre-selected auto-off control word, a signal may be sent to killswitch110 that then sendspower control signal82 tobattery system84 to shut offheadset unit14.
• In operation, the above described procedure serves to turn off the battery power forheadset unit14 unless an appropriate code signal has been recognized within the previous 60 seconds. The auto-off function may therefore be configured to turn offbattery power 60 seconds (or any other predetermined period) after the cessation of accurate IR data transmissions bytransmitter subsystem12. As described elsewhere,system10 may incorporate error detection methods. In such an embodiment, the auto-off function may also be configured to turn off battery power after a predetermined number and/or type of errors has been detected. This approach provides an advantageous auto-off function that may be used to save headset battery power by turning off the headphones a predetermined period after a radio, or other transmitter, in an automobile is turned off, perhaps by turning off the ignition of the car, or alternatively/additionally when too many transmission/reception errors have degraded audio performance to an unacceptable level.Headset unit14 may also be configured to only power down upon detection of too many errors, wherein all processing ceases and is reactivated at predetermined intervals (e.g. 30 seconds) to receive a predetermined number ofpackets86 and check for errors in these received packets.Headset unit14 may further be configured to resume full, constant operation after receiving a preselected number ofpackets86 having no, or below, a preselected number of errors.
• In an advantageous mode,kill switch110 may also be used to provide an auto-on function in the same manner by maintaining the power applied to IR receivedsignal processor72,delay counter108 andcode detector106 if the power required thereby is an acceptable minimum. Upon activation of an appropriate signal source as part oftransmitter subsystem12, the predetermined code signal may be detected andpower control signal82 sent tobattery system84 to turn on the remaining unpowered systems inheadset receiver unit14.
• Referring again toFIGS. 1 and 4, one important task in maintaining proper operation ofsystem10 is to maintain synchronization between the operations, particularly the sampling and/or A/D operations oftransmitter subsystem12 and the decoding and related operations ofheadset receiver unit14. Although synchronization may be maintained in several different ways, it has been found to be advantageous particularly for use in a system (such as system10) including a possible plurality of battery powered remote or receiver units (such as headset units14) to synchronize the timing of the operations ofheadset receiver units14 to timing information provided bytransmitter subsystem12 and included within IR signals16 to assure that the synchronization was accurately achieved for multiple receiver units that may be replaced or moved between automobiles from time to time.
• Referring still toFIGS. 4 and 5, IR data is applied from IR receivedsignal processor72 to synchdetector112 that may conveniently detectgap100 by, for example, detecting the trailing edge ofdata section88 in a particular transmittedpacket86 and, after an appropriate pre-selected delay or gap, detect the leading edge ofheader section87 of a subsequent transmittedpacket86. Simple variations of this sync signal detection may alternately be performed bysynch detector112 by combining information related to the trailing edge, gap length and/or expected data content such as all 1's or all 0's or the like and the actual or expected length of the gap and/or the leading edge.
• Upon detection of appropriate synchronization data,sync detector112 may then maintain appropriate clocking information forheadset receiver unit14 by adjusting a clock or, preferably, maintaining synchronization by updating a phase lock loop circuit (or PLL), such asPLL114. The output ofPLL114 may then be applied toDSP76 for synchronizing the decoding and/or sampling of the IR data, for example, by controlling the clock rate of the D/A conversion functions ofDSP76. The resultant synchronized signals are then applied by switchingselector78 toheadphones80. Without such synchronization, the audio quality of the sounds produced byheadphones80 may be seriously degraded.
• Another function that may be provided bydecoder74 includes updating the operation ofheadset receiver unit14. In particular, upon recognition of an appropriate update code bycode detector106, the data indata section88 from one or more subsequent transmitted signals orpackets86 may be applied bycode detector106 to an appropriate memory inheadset receiver unit14, such asrewritable memory116. The data stored inmemory116 may then be used to control subsequent operations ofheadset receiver unit14 by, for example,decoder74.
• The update function described above with respect toFIG. 4 may be used to revise or updateheadset receiver unit14 for operating modes that vary the processing of data in multiple channel format, such as variations in the 5.1 or 7.1 audio format. Other uses of the update format may be in automatically selecting the language or age appropriate format used on various audio channels to control what is provided to a particular listener.
• For example,system10 may be used in a museum to provide information, in audio format, for one or more exhibits. Before a particularheadset receiver unit14 is provided to, or rented by, a museum visitor, that headset unit might be programmed by use of the update format to provide age appropriate audio for the listener to be using the headset unit.
• Alternately, the updating may be performed upon rental of a headset unit to correspond to the audio services to be provided. A particular headset might be programmed to automatically activate upon receipt of an audio signal of a sufficient magnitude to indicate proximity to the exhibit to be described. One headset might be programmed to provide audio only for exhibits in a certain collection while other headsets might be programmed to receive all related audio. This programming or updating may easily be performed at the time of rental or other distribution for each headset.
• Another use of the updating or programming function is to permit the reprogramming of a larger number of headsets at the same time. For example, continuing to use the museum exemplar, a paging system, emergency or other notification system may be implemented with the upgrade function so that museum patrons with a selected code in their headset, or all such patrons, may be selectively paged or notified of specified information, such as museum closing times or the procedure to follow upon declaration of an emergency such as a fire. In this way, such information may be provided in real time, from a simple telephone or paging interface, by controllably switching the audio produced in one or more selected headphones rather than by altering the audio being normally produced.
• Another example of the use of the upgrade function might be to change codes that permit operation of the headphones, or related equipment, to prevent stealing or tampering with the headphones. Headphones being improperly removed from a listening chamber, such as a vehicle, may be programmed to issue a warning, to the listener or to others, upon passing through an exit. In order to prevent tampering with the headsets to foil such operations, the codes may be randomly or frequently changed.
• A further use of the upgrade function is to permit headphone units to be sold or provided for use at one level and later upgraded to a higher level of operation. As one simple example, multi-channel headphones may be distributed without coding required to perform multi channel operation. Such headphones, although desirable for single channel operation, may then temporarily or permanently upgraded for higher performance upon payment of an appropriate fee.
• Referring now toFIG. 5, top and front views of multi-channel headphones118 use withsystem10 are depicted in which leftearphone system120 andright earphone system122 are mounted onhead band124 that is used to position the earphones on the listener's head. Each of the earphone systems includes a plurality of speakers, such asfront speaker126,center speaker128 and rear speaker130 as designated onright earphone system122 together with effective aperture132 andeffective audio paths134.
• The apparent distances alongeffective audio paths134 fromspeakers126,128 and130 to effective aperture132 in each earphone are controlled to provide the desired audio experience so that both the apparent azimuthal direction and distance between each speaker as a sound source and the listener is consistent with the desired experience. For example, audio provided byspeakers126 and128 may be provided at slightly different times, with different emphasis on the leading and trailing edges of the sounds so that an apparent spatial relationship between the sound sources may be synthesized to duplicate the effect of home theater formatted performances. Although the spatial relationships for some types of sounds, like high frequency clicks, may be easier to synthesize than for other types of sounds, the effect of even partial synthesis of spatial sound relationships in a headset is startling and provides an enhanced audio experience.
• In addition to the speakers noted above for use in stereo and multiple channel stereo formats, a low frequency, non-directional monaural source, such assub woofer134, may be advantageously mounted toheadband124 to enhance the user's audio experience.
• With reference now toFIG. 6,audio transmission device500 includessingle DSP600 which may receive four digitized audio input streams602,603,604,605 multiplexed by twomultiplexers606,608 into twosignals610,612 for input into direct memory access (DMA) buffersDMA0614 andDMA1616 connected toserial ports613,615 of theDSP600. Audio streams602-605 may be digitized by analog-to-digital converters (ADCs)618,619,620,621 located for example inaudio modules622,623,624,625 shown inFIG. 7.Audio device34 andMP3 player44 ofFIG. 1 are typical examples of such audio modules. As noted above with respect toFIG. 1, audio devices utilizing multiple analog inputs provided to a single ADC, as well as multiple digital inputs that are provided directly to multiplexers such asmultiplexers606,608, may be used.
• Referring toFIG. 7, the data multiplexing circuitry ofaudio transmission device500 combines two channels ofdigitized data602,603 and604,605 into oneserial data stream610,612 respectively. The data stream slots for two differently phased digital audio stereo pairs (two stereo pairs)610,612 are combined to create one constantdigital data stream633. The left/right clocking scheme for the audio modules, described in greater detail elsewhere herein, is configured such that two stereo channels (four analog audio input lines) share one data line.Outputs602,603 and604,605 of in-phase ADCs618,620 and619,621 are multiplexed with the 90 degrees phase shifted data. The higher ordered channels (Channels3 and4) are clocked 90 degrees out of phase of the lower channels (Channels1 and2). This allows two channels pairs (Channel1 left and right andchannel3 left and right) to share a single data line. Two sets of serial digitized audio data are input toDSP600. Both odd numbered channels are on the same serial line and both even numbered channels are on the same serial line. Clock andclock phasing circuitry628 provides the input data line selection ofmultiplexers606,608.
• With continued reference toFIG. 7,DSP600, together withmultiplexers606,608, may be provided inencoder626 withintransmitter500.Encoder626 accepts the four digitizedaudio inputs602,603,604,605 fromaudio modules622,623,624,625 and usesline driver631 to send digitizedserial data stream633 toIR transmitter module634 for transmission toheadphones80.
• Encoder626 also includes clock andclock phasing circuitry628, boot/program memory630, andpower supply632.DSP600 serves as the central control for theencoder626 circuitry, including control of all inputs and outputs ofaudio transmission device500. A clocking divider provided within clockingcircuit628 is activated byDSP600 to provide signals to drive the clocks for any audio modules (e.g. ADCs) and audio data inputs to the DSP.DSP600 combinesaudio data610,612 from two serial sources (multiplexers606,608) and formats the audio data into singleserial data stream633 of data packets that is provided toline driver631 to send toIR transmitter634. In one embodiment,line driver631 may be a differential line driver with an RS485 transceiver, and an inverter may be used to invert and buffer data fromDSP600.DSP600 uses the base 10.24 MHz clock of clockingcircuit628 multiplied by a phase locked loop (PLL) internal to the DSP. In one embodiment the DSP clock speed is 8× MHz, but this may be reduced so as to reduce overall power consumption byaudio transmission device500.
• With continued reference toFIG. 7,boot memory630 stores the program memory for DSP600 (that contains the software controlling the DSP) during shut down. An 8-bit serial EEPROM may be used asboot memory630. Upon power up, the DSP may be programmed to search external memory circuits for its boot program to load and commence executing.Boot memory630 is attached to multi-channel buffered serial port615 (McBSP1) ofDSP600. In alternative embodiments, the DSP software may be provided in DSP read-only-memory (ROM).
• With reference now toFIG. 8, clock andclock phasing circuitry628 develops all clocks required byencoder626 andaudio modules622,623,624,625. Four separate clocks are required for the DSP, audio data transfer and audio digitizing. These aremaster clock660,serial clock661, left/right clock662 and multiplexer clock663. Clock phasing is also required bymultiplexers606,608 to multiplex digitized audio input streams602,603,604,605 as previously described with respect toFIG. 6.Master clock660 is used to drive the master-synchronizing clock signal for the audio digitizing modules and the DSP.Master clock signal660 is generated from stand-alonecrystal oscillator circuit660 and has bufferedoutput661. The master clock frequency is 10.24 MHz, which allows the derivation of the serial clock and left/right clock from the master clock. The serial clock is used to clock each individual bit of digitized audio input streams602,603,604,605 fromaudio modules622,623,624,625 intoDSP600.Serial clock signal661 is derived from the master clock using one-fourth clock divider667 to generate a clocking signal at a frequency of 2.56 MHz.
• The left/right clock is used to clock the Left and Right data words from digital audio data streams610,612 generated bymultiplexers606,608 for input toDSP600, and to develop the DSP frame sync. Left/right clock signals662 are derived from the master clock usingclock divider667 to generate a signal at a frequency that is256 times slower than the master clock.Clock phasing circuitry668 separates the left/right clock into two phases by providing a 90-degree phase shift for one of the left/right clocks. This allows two of the fouraudio modules622,623,624,625 to produce a 90-degree phase shifted output. The outputs of the in phase left/right clocked audio module outputs are multiplexed with the 90 degrees phase shifted data on one line. Each left/right clock phase serves as a separate frame sync for digitized audio input streams602,603,604,605 fromaudio modules622,623,624,625.
• Multiplexer clock663 is used by the multiplexer logic for toggling the selected input data lines to combine the digital audio packets in digitized audio input streams602,603,604,605 fromaudio modules622,623,624,625. Multiplexer clock signal663 is also generated byclock divider667. DSP clock signal664 is used to driveDSP600 and is generated by convertingmaster clock signal660 to a lower voltage (e.g. 1.8V from 3.3V), as required by the DSP, by buffer/voltage converter669. Other clocking schemes may be used by changing the base crystal oscillator frequency (i.e. the 9.216 MHz base clock for a 40 KHz left/right clock may be changed to a 11.2896 MHz base clock for a 44.1 KHz left/right clock).
• Power supply632 develops all of the required voltages forencoder626. In one embodiment,encoder power supply632 may accept an input voltage range from +10 VDC to +18 VDC. Four separate voltages may be used on the transmitter baseboard; Input voltage (typically +12 VDC), +5 VDC, +3.3 VDC, and +1.8 VDC. Transient protection may be used to prevent any surges or transients on the input power line. A voltage supervisor may also be used to maintain stability withDSP600. The unregulated input voltage is used as the source voltage for the +5 VDC. A regulated +5 VDC is used to supplyIR transmitter module634.Audio modules622,623,624,625 use +5 VDC for input audio protection and input audio level bias.IR transmitter634 uses +5 VDC for bias control andIR driver circuit650. Regulated +3.3 VDC is used to supplyDSP600 and logic ofencoder626, and is also supplied to the audio modules for their ADCs. The +3.3 VDC is developed from the regulated +5 VDC supply voltage and is monitored by a voltage supervisor. If the level falls below 10% of the +3.3 VDC supply, the voltage supervisor may holdDSP600 in reset until a time period such as 200 ms has passed after the voltage has increased above +3.0 VDC. Regulated +1.8 VDC is used to supply the DSP core ofencoder626 and is developed from the regulated +3.3 VDC supply voltage.
• Referring now toFIG. 9, in oneembodiment audio modules622,623,624,625 may be used to provide digitized audio input streams602,603,604,605 toDSP600. The audio modules may be external or internal plug-in modules toencoder626 or may be incorporated into the encoder. In an embodiment providing four channels of audio, four audio modules may be used with the transmitter baseboard. Each audio module, such asaudio module622 shown inFIG. 9. accepts one stereo audio pair (left and right) ofinputs638,639. Power and the master clock, serial clock, and left/right clock are all supplied byencoder626. Signal conditioning and input protection circuitry may be used to prepare thesignals638,639 prior to being digitized and protect the input circuitry against transients.
• Signals638,639 may be conditioned separately.DC Bias circuit640 sets signals638,639 to the midrange of the five-volt power supply so as to allow the input signal to be symmetric on a DC bias. In this manner, any clipping that occurs will occur equally on each positive and negative peak. InputSurge Protection circuit641 may be used to protect the input circuitry against transients and over voltage conditions. Transient protection may be provided by two back-to-back diodes in signal conditioning andinput protection circuit640 to shunt any high voltages to power and to ground. Line level inputs may be limited to two volts, or some other practicable value, peak to peak.Low pass filter642 may be provided to serve as a prefilter to increase the stopband attenuation of the D/A internal filter. In one embodiment, each analog input audio channel frequency is 20 Hz to 18 KHz and thelow pass filter642 corner frequency is above 140 KHz so that it has minimal effect on the band pass of the audio input.
• With continued reference toFIG. 9,ADC643 is used to digitize both left andright analog inputs638,639. Single serialdigital data stream602 containing both the left and right channels is output byADC643 toencoder626. The 10.24 MHz master clock is used to develop the timing forADC643, and the 2.56 MHz serial data clock is used to clock the data from the ADC. The 40 KHz left/right clock is used to frame the data into distinct audio samples. Each left and right analog sample may be a 16-bit value.
• With reference now toFIG. 10, IR transmitter ormodule634 convertsdigital data stream633 to IR (Infrared) transmission signals16. PPM (Pulse Position Modulation) encoding is used to increase transmitter power by using a bit position value.IR transmitter634 includesline receiver650 to receive differential RS485 signal633 fromline driver631 and transform it into a single ended data stream. The data stream is then buffered and transferred to infrared bias andcontrol circuits650, which drives the light emitting diode(s) (LEDs) ofemitters652 and controls the amount of energy transmitted.IR transmitter634 includes four infrared bias andcontrol circuits650 and fourrespective emitters652, with a 25% duty cycle for eachemitter652. Bias control maintains the IR emitter(s) in a very low power-on state when a zero bit is sensed indata stream633 to allow the direct diode drive to instantly apply full power to the IR emitter diodes when a positive pulse (one bit) is sensed. A sensing resistor is used to monitor the amount of current supplied to the diodes so that when the emitter diode driver is pulsed, the bias control maintains a constant current flow through the diodes.IR emitters652 transformdigital data stream633 into pulses of infrared energy using any practicable number (e.g. four per IR emitter) of IR emitter diodes. The bandwidth of the electrical data pulses are mainly limited by the fundamental frequency of the square wave pulses applied to the IR emitter diodes due to the physical characteristics of the diodes. In one embodiment, the IR energy may be focused on a center wavelength of 870 nM.Encoder626 supplies all power toIR transmitter module634. +5 VDC is used for driver andbias control circuitry650. In one embodiment,encoder626 supplies PPM-encodeddigital data stream633 toIR transmitter634 at 11.52 Mb/s.
• Referring now toFIG. 11,MCBSPs613,615 andDMAs614,616 are used to independently gather four stereo (eight mono) channels of data. When either of the McBSPs has received a complete 16-bit data word, the respective DMA transfers the data word into one of two holdingbuffers670,671 (for DMA1616) or672,673 (for DMA0614) for a total of four holding buffers. EachMcBSP613,615 uses it'sown DMA614,616 andbuffer pair672/673,670/671 to move and store the digitized data. While one buffer is being filled,DSP600 is processing the complementary buffer. Each buffer stores twenty-five left and twenty-five right data samples from two different ADCs (for a total of 100 16-bit samples). Each word received by each McBSP increments the memory address of the respective DMA. When each buffer is full, an interrupt is sent from the respective DMA toDSP600.DSP600 resets the DMA address and the other buffer is filled again with a new set of data. This process is continuously repeated.
• DSP600 creates two transmit buffers that are each the size of a full transmitpacket86. In one embodiment, 450 (16-bit) words are used in each packet (as more fully discussed below). When apacket86 is first initialized, static header/trailer values are inserted in the packet. For the initial packet and subsequent packets, the User ID/Special Options/Channel Status (USC) values ofcontrol block96, data offsets, dynamic header values, and channel audio data are added to each packet. The USC values calculated from the previous packet audio data are preferably used. The audio data is PPM encoded and placed in data blocks packet. Once a predetermined number (e.g. twenty-five) of samples from each channel have been processed,packet86 is complete.
• WhenDSP600 fills one of the output buffers completely, a transmission DMA (DMA2) is enabled. DMA2 then transfers the data in the filled output buffer to a serial port (McBSP0) oftransmission device500. McBSP0 in turn sendsserial data633 toline driver631 to send toIR transmitter634. Once the Output DMA and McBSP are started, they operate continuously. WhileDSP600 fills one of the buffers, the other buffer is emptied by DMA2 and sent to McBSP0. Synchronization is maintained via the input data.
• DSP600 handles interrupts fromDMAs614,616, monitors Special Options and Channel Status information as described elsewhere herein, constructs each individual signal (or transmission packet)86, and combines and modulates the audio data and packet information. The DMA interrupts serve to informDSP600 that the input audio buffer is full, at which time the DSP reconfigures the respective DMA to begin filling the alternate holding buffer and then begins to process the “full” holding buffer. No interrupt is used on the output DMA. Once the output buffer is full, the output DMA is started to commence filling the other buffer.
• As more fully described elsewhere herein, Special Options information may be used to indicate ifaudio transmission device500 is being used in a unique configuration and may be provided through hardware switches or hard coded in the firmware. Special Options may include, but are not limited to, 5.1 and 7.1 Surround Sound processing. In one embodiment, four bits may be used to indicate the status of the Special Options. Four bits will provide for up to four user selectable switch(es) or up to fifteen hard coded Special Options. The Headphone normal operation may be a reserved option designated as 0000h.
• When a switch option is used, a minimum of one or more of the fifteen Special Options will be unavailable for additional options (i.e. if two switches are used, only four additional Special Options may be available. If four switches are used, no additional Special Options may be available.) For instance, to utilize a 5.1 or 7.1 Surround Sound option, a hardware switch may be used to toggle a bit level on a HPI (Host Port Interface) ofDSP600. A one (high) on the HPI may indicate that an option is used. A zero (low) on the HPI may indicate normal four-channel operation.DSP600 may read the HPI port and set the appropriate bit in the Special Options value.
• Channel Status information may be used to indicate which stereo channels (left and right channels) contain active audio data. The amplitude of the digital audio data may determine whether a stereo channel is active or inactive. If active audio is not detected on a stereo channel, the Channel Status can be flagged in the outgoing packets as OFF (zero). If active audio is sensed on a stereo channel the Channel Status can be flagged in the outgoing packets as ON (one).
• In one embodiment, to determine if a stereo channel is active, the absolute values for each set of the four stereo channel data samples are accumulated. Twenty-five samples (the number of individual channel data samples in one packet) of each left channel and each right channel are combined and accumulated. If the sum of the stereo channel samples exceeds the audio threshold, the Channel Status may be tagged as active. If the total of the stereo channel samples does not exceed the audio threshold, the Channel Status may be tagged as inactive. Four bits (one for each stereo channel) may be used to indicate the stereo Channel Status and preferably are updated each time a packet is created.
• Referring toFIG. 12, an embodiment for encoding the four channels into individual signals ortransmission packets86 is shown to partition eachsignal86 intoheader section87 anddata section88.Header section87 contains all of the information for receiver700 (detailed herein below) to sense, synchronize and verify the start of avalid transmission packet86. In one embodiment, the header section includes Preamble, Terminator, and Gap values that are not PPM encoded, and further includes Product Identifier and Data Offset values that are PPM encoded.
• Gap value90 may be a 32-bit (double word) value used byreceiver700 tosense header section87 and synchronize withtransmission packet86.Gap90 may be composed of a Sense Gap, a Trigger Gap, and a Sync Gap. The Gap is preferably not PPM encoded and is a static value that is never changed. The first part ofGap90 is the Sense Gap, which contains seven leading zeros. These bits are used byreceiver700 to recognize the beginning of the Gap period. The second part ofGap90 is the Trigger Gap, which contains alternating one and zero bits. These bits are byreceiver700 to stabilize the clock recovery circuitry over the Gap period. The third part of the Gap is the Sync Gap, which contains three zero bits. These bits are used byreceiver700 to mark the beginning of eachtransmission packet86.
• Preamble PRE may consist of a predetermined number of equal values (e.g. AAAA hexadecimal) to further enable synchronization ofreceiver700 withtransmitter500. The preamble consists of two separate 16-bit (double word) values89,91 and are used byreceiver700 to identify the start of eachpacket86.Preamble1word89 is also used to assist in stabilizing the clock recovery circuitry. The Preamble is not PPM encoded and may be a static value that is never changed.Preamble1word89 is preferably placed at the start ofpacket86 andpreamble2word91 preferably followsGap90.Preamble words1 and2 are composed of alternating ones and zeros (AAAAh). The first “one” bit of thePreamble2word91 may signal the start of theparticular packet86.
• Following thePreamble2word91 is predetermined code or unique identifier ID (PID)92, which may be selected to uniquely identifytransmitter500 toreceiver700.PID92 is preferably PPM encoded and is a static value that does not change. This feature may be used, for example, to prepare headphones that may only be used in a car, or limited to use with a particular make of car, or with a particular make of transmitter. Thus, for headphones used in a museum wherein visitors rent the headphones, the receivers in the headphones may be programmed to become operation only upon detection of a unique identifier ID that is transmitted only bytransmitters500 installed in the museum. This feature would discourage a visitor from misappropriating the headphones because the headphones would simply not be functional anywhere outside of the museum. This feature may further be used to control quality of after market accessories by an OEM. For instance, a vehicle manufacturer or a car audio system manufacturer may install transmitters in their equipment but control the licensing/distribution of the unique ID transmitted by their equipment to those accessory (headphones, loudspeakers, etc.) manufacturers that meet the OEM's particular requirements.
• FollowingPID92 is data offset value (DO)93 followed by offsetportion94, the final portion ofheader section87. Offsetvalue93 indicates the length of (i.e. number of words in) offsetportion94 anddata filler portion97, and may be a fixed value that is constant and equal in each transmitted signal orpacket86, or alternatively may be dynamically varied, either randomly or according to a predetermined scheme. Varying the length of the offset portion from signal to signal may help avoid fixed-frequency transmission and/or reception errors and reduce burst noise effects. Offsetportion94 anddata filler portion97 together preferably contain the same number of words (e.g. 30), and thereby allow the random placement of data section within aparticular packet86 while maintaining a constant overall length for all packets. Offsetportion94 serves to spaceunique PID92 fromdata section88 and may contain various data. This data may be unused and thus composed of all random values, or all zero values, to be discarded or ignored byreceiver700. Alternatively, offsetportion94 may contain data used for error detection and/or error correction, such as values indicative of the audio data or properties of the audio data contained indata section88.
• Data section88 is formed by interleaving data blocks95 with control blocks96. In one embodiment data block95 consist of 5 samples of 4 channels of left and right encoded 16-bit values (1 word) of audio information, for a total of 80 PPM-encoded words. Data blocks95 may consist of any other number of words. Furthermore, the data blocks in eachsignal86 transmitted bytransmitter500 do not have to contain equal numbers of words but rather may each contain a number of words that varies from signal to signal, either randomly or according to a predetermined scheme. Consecutive data blocks95 within asingle packet86 may also vary in length. Additionally,consecutive packets86 may contain varying numbers of data blocks95 in theirdata sections88. Indicators representing, e.g., the number of data blocks and the number of words contained in each data block may be included inheader block87 of eachpacket86, such as in offsetportion94, to enabletransmitter700 to properly process the data contained in eachpacket86.
• Control block96 follows eachdata block95, and in one embodiment includes the Special Options and Channel Status information discussed previously, as well as a predetermined code or unique identifier User ID. As described elsewhere herein, User ID may be a value used for error detection, such as by comparing a User ID value contained inheader87 with each successive User ID value encountered in subsequent control blocks96. If the values of User ID throughout apacket86 are not identical, the packet may be discarded as a bad packet and the audio output of the headphones may be disabled after a predetermined number of sequential bad packets has been received. The User ID may further be used to differentiate betweenvarious transmission devices500 such that, for instance, areceiver700 programmed for use with a transmission device installed in a particular manufacturer's automobile will not be useable with the transmission devices in any other manufacturers automobiles or in a building such as a museum or a private home (as further detailed elsewhere herein). Channel Status information may be used to control the channel selection switch onreceiver700 to only allow selection of an active channel, and to minimize power consumption by powering down the receiver DSP to avoid processing data words in eachpacket86 that are associated with an inactive channel, as more fully described elsewhere in the specification.
• At the end ofdata section88 istrailer99 which may includedata filler97 and end block or terminator block (TRM)98.TRM98 may preferably a 16-bit (single word) value and may be used byreceiver700 to allow a brief amount of time to reconfigure the McBSP parameters and prepare for anew packet86.TRM98 may also be used to assist in stabilizing thereceiver700 hardware clock recovery over theGAP90 period, and may also contain data for error detection and/or correction, as discussed elsewhere.TRM98 is preferably not PPM encoded and is a static value preferably composed of alternating ones and zeros (AAAAh).
• With reference now toFIG. 13, receiver apparatus orheadset unit700 has two separate sections to enable omni-directivity of reception and to more evenly distribute the circuitry of the receiver throughout the enclosure ofheadphones80. The main section of the receiver isprimary receiver702. The secondary module issecondary receiver704. Bothprimary receiver702 andsecondary receiver704 contain an IR receiver preamplifier. In one embodiment,primary receiver702 may contain the bulk of the receiver circuitry andsecondary receiver702 may be used as a supplementary preamplifier forIR signal16 when the primary receiver IR receiver is not within line of sight of the transmitted IR signal due to the orientation or location of thelistener wearing headphones80.
• Referring toFIG. 14,primary receiver702 containsreceiver DSP710, IR receiver/AGC714, dataclock recovery circuit716, D/A converter (DAC) andaudio amplifier circuit722, user selectable switches and indicators controlcircuit718, boot/program memory730, and power supply andvoltage supervisor circuit740.DSP710 serves as the central control for thereceiver700 circuitry and controls all of the inputs and outputs of the receiver. The IR data packet is received byDSP710 in singleserial stream712 fromIR receiver714. The start ofIR data stream712 creates the frame synchronization for the incoming data packet.Clock recovery circuit716 develops the IR data clock used to sample the IR data. The DSP serial port completes clocking for the 16-bit DAC. The master clock for the 16-bit D/A converter is developed from an additional serial port.
• External switches andindicators719 may include switches to allow the listener to access functions such as select the desired channel and adjust the audio volume. LED indicators may be provided to be driven byDSP710 to indicate whether power is supplied to the receiver and the selected channel.Control circuit718 interfaces external switches andindicators719 withDSP710, providing input from the switches to the DSP and controlling the indicators as dictated by the DSP.
• The base clocking forDSP710 may be developed fromclock recovery circuit716. The input clock toDSP710 is multiplied by a PLL internal to the DSP. The DSP clock speed may be 8× MHz, and may be reduced to minimize overall power consumption byreceiver700.DSP710 can also disable the switching power supply onsecondary receiver704 via a transistor and a flip-flop. If the software does not detect a valid signal in a set amount of time, the DSP can disable the switching power supply and remove power from the receiver, as detailed elsewhere herein.
• Referring now toFIG. 15, IR Receiver/AGC714 is used to transform and amplify the infrared data contained in receivedsignal16. IR Receiver/AGC714 also controls the amplification and developsdigital data stream712 forDSP710 and dataclock recovery circuit716. The usable distance for the IR receiver is dependent on variables such astransmitter500 power and ambient lighting conditions. In one embodiment, the overall gain of IR Receiver/AGC714 may be approximately 70 dB.
• With continued reference toFIG. 15, IR receiver/AGC circuit714 containspreamplifier770,final amplifier771, data squaring stage (or data slicer)772, and AGC (Automatic Gain Control) circuit773.IR preamplifier770 transformsoptical signal16 into an electrical signal and provides the first stage of amplification. The IR preamplifier is composed of three separate amplifiers. The first amplifier is composed of four IR photo detector diodes and a transimpedance amplifier. In one embodiment, combined wide viewing angle photo diodes may produce better than 120 degrees of horizontal axis reception and 180 degrees of vertical axis reception. A daylight filter may be incorporated into the photo detector diode that, together with inductive transimpedance amplifier feed back, minimizes the DC bias effect of ambient lighting. When IR signal16 is transmitted, a current pulse proportional to the strength of the IR signal is generated in the photo detector diodes. The strength of the received IR signal is dependent on the distance from the transmitted IR source.
• The current pulse from the photo diodes is applied directly to the transimpedance amplifier. The transimpedance amplifier senses the rising and falling edges of the current pulse from the photo detector diodes and converts each pulse into a voltage “cycle.” The second amplifier is a basic voltage amplifier. The output of the second stage is controlled by AGC circuit773. The third amplifier is also a basic voltage amplifier. The output of the third stage ofpreamplifier770 is fed the input offinal amplifier stage771 and AGC773.
• Final amplifier stage771 is used to further increase the gain of receivedIR signal16 and also serves as a combiner for Headphone—Left and Headphone—Right preamplifiers750,770.Final amplifier771 is composed of two basic voltage amplifiers. Each of the two stages of amplification increases the gain of the received IR signal. The input signal to the final amplifier is also controlled by the second stage of AGC773, as described below. The output of the final amplifier stage is fed to AGC773 anddata squaring stage772.
• AGC773 controls the amplified IR signal level. The AGC circuitry may be composed of one amplifier and three separate control transistors. The three separate control transistors comprise two levels of AGC control. The first level of AGC control uses two AGC control transistors (one for each stage) and is performed after the first voltage amplifier in both the Headphone—Left and Headphone—Right preamplifier stages750,770. The second level of AGC control occurs at the junction of both ofpreamplifier750,770 output stages and the input tofinal amplifier stage771. To develop the AGC DC bias voltage, the positive peaks of the IR signal from the final amplifier stage output are rectified and filtered. The DC signal is amplified by an operational amplifier. The value of the amplified DC voltage is dependent on the received signal strength (i.e. proportional to the distance fromIR emitters652 of transmission device500). The AGC transistor resistance is controlled by the DC bias and is dependent on the received signal strength. When the signal strength increases, the bias on the AGC transistors increases and the signal is further attenuated. AGC773 thus produces a stable analog signal fordata squaring stage772.
• Data squaring stage772 produces a digitized bi-level—square wave (i.e. composed of ones and zeros) from the analog IR signal. The input from the data squaring stage is received from the output offinal amplifier stage771. The data squaring stage compares thefinal amplifier771 output voltage “cycle” to a positive and negative threshold level. When the positive peak of the final amplifier output exceeds the positive threshold level, a high pulse (one bit) is developed. When the negative peak exceeds the negative threshold level, a low pulse (zero bit) is developed. Hysteresis is accounted for to prevent noise from erratically changing the output levels. The output ofdata squaring stage772 is sent toclock recovery circuit716 and asIR data input720 toDSP710.
• Dataclock recovery circuit716 is used to reproduce the data clock used bytransmitter500. In one embodiment ofreceiver700, the data clock recovery circuit contains an edge detector and a PLL (Phase Lock Loop). The dataclock recovery circuit716 utilizes the PLL to generate and synchronize the data clock with theincoming IR data720. The edge detector is used to produce a pulse with each rising or falling bit edge so as to create a double pulse for additional data samples for the PLL. A short pulse is output from the edge detector when a rising or falling pulse edge is sensed. The output from the edge detector is fed to the PLL.
• The PLL is used to generate a synchronized clock, which is used byDSP710 to sample the IR data signal712. A frequency and phase charge pump comparator circuit in the PLL compares the edge detector signal to a VCO (Voltage Controlled Oscillator) clock output from the PLL. The output of the comparator is sent to a low pass filter. The low pass filter also incorporates pulse storage. The pulse storage is required since the data is PPM (Pulse Position Modulated) and does not provide a constant input to the PLL comparator. The low pass filter produces a DC voltage used by the VCO of the PLL. The VCO produces an output frequency proportional to the DC voltage generated by the low pass filter. When the voltage from the loop filter rises the VCO frequency also rises, and visa versa. When the clock output of the VCO is synchronized with edge detector output, the low pass filter voltage and VCO frequency stabilize. The VCO frequency remains locked in sync with the edge detector until a phase or frequency difference develops between the VCO frequency and the edge detector signal. The output of the VCO is used as the data sample clock for serial port711 ofDSP710 and it is also used as the base clock frequency of the DSP.Receiver DSP710 uses the recovered data clock to synchronize withtransmitter DSP600 so that the data encoded and transmitted bytransmitter500 is received and decoded byreceiver500 at the same rate. The PLL also contains a lock detect, which can be used to signalDSP710 when the PLL is locked (synchronized with the incoming data). Thus, the incoming data clock is recovered continuously byreceiver500 as the incoming data packets are processed, not just when the header of each data packet is processed.
• With now reference toFIG. 16, an alternative embodiment ofreceiver700 includes dataclock recovery circuit716 that does not utilize a PLL but rather employsedge detector775,crystal oscillator776 tuned to the frequency of theaudio transmission device500 master clock, and buffers777,778 to synchronize the data clock withincoming IR data712.Edge detector775 is used to produce a pulse with each rising bit edge. A combination of four NOR gates are used to create a short pulse that is output by the edge detector when a rising edge is sensed. This provides a synchronizing edge forcrystal oscillator776. The first NOR gate of the edge detector provides a true inversion to the data stream. The output from the first NOR gate is sent to a serial port ofDSP710. The second NOR gate provides a buffer/delay. The output from the second NOR gate is fed to a RC time constant (delay). The third NOR gate triggers from the RC time constant (delay). The fourth NOR gate collects the outputs of the first and third gates. This provides a short sync pulse forcrystal oscillator776.
• Crystal oscillator776 and buffer stages777,778 provide a bi-level clock for sampling theIR data712. The crystal oscillator utilizes a crystal frequency matched to theoutgoing transmission device500 data clock frequency. A parallel crystal with an inverter is used to provide a free running oscillator. The pulse developed from the edge detector provides synchronization with receiveddata stream712. Two inverter/buffers777,778 are used to provide isolation forcrystal oscillator776. The buffered output is sent to the DSP serial port data clock input and voltage conversion buffers. The voltage conversion buffers decrease the clock peak level to 1.8 volts for the DSP core clock input.
• With reference now toFIG. 17, DAC andaudio amplifier circuit722 developsanalog signal724 fromdigitized data stream721 output byDSP710, and further amplifies and buffers the output toheadphone speakers81,83. DAC andaudio amplifier circuit722 includesDAC780, which may be a 16-bit DAC, for receiving serial digitalaudio data stream721 from DSP serial port transmitter713 (from the channel selected byDSP710 in accordance with listener selection via switches719) to produce separate left and right analog signals724 from digitalserial data stream721. Thedigital data stream721 is converted essentially in a reverse order from the analog-to-digital conversion process inaudio modules622,623,624,625. The output ofDAC780 is sent through low pass filter781 (to remove any high frequencies developed by the DAC) toaudio amplifier782.Audio amplifier782 amplifies the audio signal and provides a buffer between theheadphones80 andDAC780. The output fromaudio amplifier782 is coupled intoheadphone speakers81,83.
• User selectable switches718, shown for example inFIG. 14, allow a listener to adjust the audio volume inheadphone speakers81,83 and change the audio channel. LEDs (Light Emitting Diodes) may be used to indicate the selected channel. Two manually operated selector switches may be used to adjust the volume. One press of an up volume button sends a low pulse toDSP710 upon which the DSP increases the digital audio data volume by one level having a predetermined value. One press of a down volume button sends a low pulse to the DSP and the DSP decreases the digital audio data volume by one level. Other switch configurations may also be used. A preselected number, such as eight, of total volume levels may be provided by the DSP. All buttons may use an RC (resistor/capacitor) time constant for switch debouncing.
• A manually operated selector switch may be used by the listener to select the desired audio channel. One press of the channel selector button sends a low pulse toDSP710 and the DSP increases the channel data referred to the audio output (via DSP serial port transmitter713). A predetermined number (e.g. four or eight) different channels are selectable. When the highest channel is reached, the DSP rolls over to the lowest channel (e.g. channel four rolls into channel one). Alternatively, if a channel is not available, the DSP may be programmed to automatically skip over the unavailable channel to the next available channel such that the listener never encounters any ‘dead’ channels but rather always selects among active channels, i.e. channels presently streaming audio. A plurality of LEDs (e.g. a number equal to the number of available channels, such as four) may be used to indicate the selected channel. The illumination of one of the LEDs may also indicate that power is supplied to the circuitry and thatDSP710 is functioning. Alternatively, an LCD or other type of display may indicate the channel selected, volume level, and any other information. Such information may be encoded in the header of each data packet, and may include additional data regarding the selected audio stream (e.g. artist, song name, album name, encoding rate, etc.) as well as any other type of information such as content being streamed on the other available channels, identification of the available (versus unavailable or ‘dead’ channels), environmental variables (speed, temperature, time, date), and messages (e.g. advertising messages). The information displayed may include text and graphics, and may be static or animated.
• Referring once again toFIG. 14,boot memory730 stores the program memory forDSP710 during shut down. An 8-bit serial EEPROM connected toserial port715 ofDSP710 may be used to store the DSP program. Upon power-up the DSP may be configured to search for external memory to retrieve and load its operating software. Alternatively, the program may be provided in DSP read-only-memory (ROM).
• With continued reference toFIG. 14 and also referring toFIG. 18,power supply740 on theprimary receiver702 circuit board receivesDC power761 from switchingpower supply760 insecondary receiver704.Power supply640 receives DC power from supply759 (e.g. AAA batteries or any other type or size of batteries, or alternatively DC via a power cord from a vehicle or building power system, or any other practicable power supply) and includes a +1.8V (or other voltage, as required by the DSP circuitry) supply and associated voltage supervisor. The regulated +1.8V DC is used to supply the DSP core ofDSP710 and is developed from a regulated +3.3 VDC supply voltage. A voltage supervisor is used to monitor the +3.3 VDC. If the level drops below 10% of the +3.3V DC supply, the voltage supervisor may hold the DSP in reset. If the level falls below 10% of the +3.3 VDC supply, the voltage supervisor may holdDSP710 in reset until a time period such as 200 ms has passed after the voltage has increased above +3.0 VDC.
• With continued reference toFIG. 18,secondary receiver704 suppliespower761 toreceiver system700 and works as a supplementary preamplifier forIR signal701 when primaryreceiver IR receiver714 is not within a direct line of sight of transmittedIR signal16.Secondary receiver704 includesIR receiver preamplifier750, switchingpower supply760, and on/offswitch762.IR receiver preamplifier750 amplifiesIR analog signal16 when line-of-sight is not available to primaryreceiver IR receiver714. The two stages of the secondary receiver IR receiver preamplifier are the same as inprimary receiver702, and the output of the second stage is provided to the input of AGC773 in IR receiver andAGC circuit714 ofprimary receiver702.
• Switching power supply760 convertsbattery759 voltage to the level used by thereceiver700 circuitry. The majority of secondary receiver and primary receiver circuitry operates on 3.3 VDC at less than 200 mA. The switching supply generates 3.3 VDC from twoAAA batteries759.Switching power supply760 is able to source power frombatteries759 down to 0.9 volts utilizing a charge pump (inductor-less), or alternatively a boost-type converter. A low pass filter may be used to remove the high frequency components of switchingpower supply760.
• On/offswitch762 enables and disables switchingpower supply760. The on/offswitch circuit762 is powered directly bybatteries759.Inputs718 to on/offswitch circuit762 include a manually operated switch andDSP710. A manually operated SPST (Single Pole Single Throw) switch is connected to the clock input of a flip-flop, wherein each press of the SPST switch toggles the flip-flop. A RC (resistor/capacitor) time constant is used to reduce the ringing and transients from the SPST switch. A high output from the flip-flop enables switchingpower supply760. A low output from the flip-flop disables switchingpower supply760 and effectively removes power from thereceiver700 circuit.DSP710 can also control the action of the flip-flop. If the software does not detect a valid signal in a set amount of time,DSP710 may drive a transistor to toggle the flip-flop in a manner similar to the manually operated SPST switch.
• With reference once again toFIG. 14, inoperation DSP710 activates an internal DMA buffer to move the PPM4-encoded data received on the serial port (McBSP)711 to one of two received data buffers. Once all 25 samples of a data packet have been collected, a flag is set to trigger data processing. When the receive buffer “filled” flag is set, data processing begins. This includes PPM4-decoding the selected channel of data, combining the high and low bytes into a 16-bit word, attenuating the volume based on listener selection, and placing the decoded left and right digitized values for all 25 samples into an output buffer DacBuffer. A flag is set when the output buffer is filled, and a second DMA continually loops through the output buffer to move the current data to serial port (McBSP)transmitter713 for transmission toDAC circuit722.
• Serial port receiver711 is used for capturing the IR data. The receiver clock (CLKR) and frame synchronization (FSR) are from external sources. The receiver is configured as single-phase, 1-word, 8-bit frame, 0-bit delay, and data MSB first. Received frame-sync pulses after the first received pulse are ignored. Received data is sampled on a falling edge of the receiver clock.
• Serial port transmitter713 is used to presentdata721 toDAC circuit722 for audio output toheadphone speakers81,83. The transmitter clock (CLKX) and frame synchronization (FSX) are generated internally on a continuous basis, as previously described. The transmitter is configured as single-phase, 4-word, 16-bit frame, 0-bit delay, and data MSB first. Transmit data is sampled on a rising edge of the transmitter clock.
• The sample-rate generator of serial port711 is used withDAC circuit722 andserial port transmitter713. The sample rate generator uses divide-by-9 of theDSP710 clock to achieve a frequency of 8.192 MHz. The transmit frame-sync signal is driven by the sample rate generator with a frame period of 64 clock cycles, and a frame width of 32. The sample-rate generator of serial port711 is the master clock. The sample rate generator uses divide-by-4 of theDSP710 clock. The transmit frame-sync signal is driven by the sample rate generator with a frame period of 16 clock cycles.
• The DMA buffers ofreceiver700 are configured generally similarly to those oftransmitter500. The DMA priority and control register also contains the two-bit INT0SEL register used to determine the multiplexed interrupt selection, which should be set to 10b to enable interrupts forDMA0 and1. DMA0 is used to transferIR data712 received using the receiver of serial port711 to one of two buffers. The source is a serial port711 receive register DRR1_0. The destination switches between one of two received data buffers, RxBuffer1 and RxBuffer2. The counter is set to the size of each buffer, which may be 408 words. The sync event is REVT0 in double word mode for 32-bit transfers. The transfer mode control is set for multi-frame mode, interrupt at completion of block transfer, and post-increment the destination.DMA2 is used to transfer the single channel of digital audio toDAC circuit722. The source is the DSP output buffer DacBuffer. The destination is aserial port713 transmitter register DXR1_0. The counter is set to the size of the DacBuffer, which may be 4 words. The sync event is XEVT0. The transfer mode control is set for autobuffer mode, interrupts generated at half and full buffer, and post-increment the source.
• The serial port711 receiver ISR is used to check whether data stream712 in synchronized. A received data state machine begins in dwell mode where the received data is examined to determine when synchronization is achieved. Normal operation begins only after synchronization. The serial port711 receiver ISR first checks forpreamble91 PRE in datastream header block90 as shown inFIG. 12. When this synchronization is detected, the receiver of serial port711 is set to a dual-phase frame: the first phase is 128 32-bit words per frame with no frame ignore, the second phase is 73 32-bit words per frame with no frame ignore. This combinations produces the equivalent of 402 16-bit words. The state machine proceeds to check that subsequently received words form a predetermined code. When this synchronization is detected, DMA0 is initialized with its counter length set to half the size of the receive buffer, RxBuffer, which is 408/2=204 words. The destination is then set to the current receive buffer, RxBuffer1 or RxBuffer2. Next DMA0 is enabled and the serial port711 receiver ISR is turned off. The state machine is placed in dwell mode in advance of the next loss of synchronization. If the data stream goes out of sync, the serial port711 receiver is set to a single-phase, 4-word, 8-bit frame with no frame ignore, and the serial port711 receiver ISR is turned on.
• If the predetermined code is not detected, a reception error may be presumed to have occurred and a counter withinDSP710 may be initialized to count the number of packets received wherein the encoded value is not detected. After a preselected number of such occurrences are counted the DSP may mute the audio output to the headphones. Muting based on detection of a preselected number of such occurrences eliminates buzzing and popping sounds, and intermittent sound cut-off that can occur when repeated reception errors are encountered. The DSP may be programmed to mute the audio output after the first error is encountered, or after a larger number of errors (e.g. 10, 50, 100, etc.) have been counted. Upon muting the audio output to the headphones, the DSP waits for the next packet where the code is detected and then either provides the audio output the headphones once again or waits until a predetermined number of data packets with no errors have been received, at which time it may be presumed that the reasons that led to the previous reception errors are no longer present and the system is once again capable of clear reception. If a packet with no errors is not received for a certain time (e.g. 60 seconds) the DSP may initiate the auto-off feature and power offreceiver700, at which time the listener would have to activatemanual switch762 to turn the system back on again. Additionally, the auto-mute or auto-off features may be engaged if a predetermined amount of time passes and no headers are processed at all, due to theaudio device34 being turned off or to noise (e.g. bright light interfering with photoreception).
• When DMA0 completes its transfer, the synchronization procedure is restarted. DMA0 is turned off, the serial port711 receiver is turned on, and the current buffer index is toggled to indicate RxBuffer1 or RxBuffer2. A flag is next set indicating that the DMA transfer is complete. A main loop inDSP710 waits for a flag to be set (in DMA0 ISR) indicating that a packet containing the 4 channels of audio has been received and transferred to one of two receive buffers. When this flag is set, output processing byDSP710 commences. Output processing consists of determining the current buffer based on the buffer index, then using the selected channel data to retrieve and decode the PPM4-encoded left and right channel data. The selected volume level is applied to attenuate the digital signal, and then the final digital signal for the left and right earphones is placed in a current outgoing data block for transmission to DAC circuit for conversion and amplification as described previously with reference toFIG. 14.
• Numerous modifications and additions may be made to the embodiments disclosed herein without departing from the spirit or scope of the present inventions including hardware and software modifications, additional features and functions, and uses other than, or in addition to, audio streaming.
• Referring now toFIG. 19,vehicle800 such as an automobile, bus, train car, naval vessel, airplane or other suitable vehicle may include factory-installed, or aftermarket installedaudio device34, which may be a typical in-dash head unit comprising a radio tuner, a cd player or a cassette tape player, and an amplifier.Audio device34 is shown powered by power system802 (e.g. battery, alternator, etc.) ofvehicle800.
• Communication system801 may be added tovehicle800 and includes plug-inunit820 that containstransmitter subsystem12 andIR transmitter driver22, and is connected toaudio device34 to receive at least one channel of stereophonic audio data therefrom. Other sources of data, e.g. a video device such asDVD player832 and an audio device such asMP3 player834, may be connected to plug-inunit820. The plug-in unit may accept digital and analog data, as previously described, and is preferably powered byaudio device34.Communication system820 further includestransmitter806 containing IR light emitting diode (LED)20, andwiring harness804 to connect plug-inunit820 withtransmitter806. Alternatively the entireIR transmitter section18, including IR transmitter orLED20 andIR transmitter driver22, may be contained withintransmitter806.
• As previously described,transmitter subsystem12 receives multiple channels of audio data and generates a single digitized audio signal. The digitized audio signal is provided toIR transmitter driver22 which generates an appropriate electric current to operateLED20 to emit IR signals16. IfIR transmitter driver22 is contained within plug-inunit820, then this electric current is carried by wiringharness804 toLED20 intransmitter806. Alternatively, ifIR transmitter driver22 is contained withintransmitter806, then the digitized audio signal generated bytransmitter subsystem12 is carried by wiringharness804 to the IR transmitter driver.
• This segmented design ofcommunication system801, including three discrete components (plug-inunit820,wiring harness804, and transmitter806) offers ease of installation ofsystem801 invehicle800 as a factory option or as an after-market addition after the vehicle has left the factory. Plug-inunit820 may be installed in the dashboard of the vehicle and may utilize a single connection to the in-dash head unit oraudio device34, and optionally a connection to each additional audio source. Alternatively,audio device34 may be capable of providing multiple concurrent channels of audio to plug-inunit820, in which configuration a single connection toaudio device34 is required.
• Transmitter806 must be installed at a location that will provide a sufficiently broad direct line-of-sight to the rear of the vehicle.Transmitter806 may be installed within a dome light enclosure ofvehicle800. Such installation may be further facilitated by incorporatingIR transmitter driver22 within plug-inunit820, thereby renderingtransmitter806 relatively small because it contains nothing more thanLED20.Wiring harness804 is also relatively small because it only needs to contain a small number of wires to carry a digitized signal to either be amplified byIR transmitter driver22 or to directly operateLED20. In either case, the electric current carried by wiringharness804 is very low voltage and wattage, and wiring harness is preferably formed with a small cross-section that further simplifies installation invehicle800 because it can easily follow tortuous paths and requires limited space.
• With continued reference toFIG. 19,system801 further includes devices equipped to receivesignals16, such asheadset unit14 andloudspeaker842. The headset units and/or loudspeaker may both be equipped with anIR receiver70 to receive IR signals16 fromtransmitter806. The headset units are described in detail elsewhere herein.Loudspeaker842 is equipped with similar circuitry including IR receivedsignal processor72,decoder74 with clock, de-multiplexer and controller,DSP76 for digital to analog conversion, as well as one or more amplifiers to amplify the selected channel.
• In an alternative embodiment,loudspeaker842 may not include achannel switching selector78 but rather may be preprogrammed to always play a preselected channel, e.g., the channel selected at the head unit. In addition, due to higher power requirements,loudspeaker842 is preferably powered via a cable by the vehicle power system802 (not shown inFIG. 19). Alternatively,loudspeaker842 may be preprogrammed to automatically cut-in and play a priority channel for communication between the driver and the passengers or an emergency channel such as a baby monitor or cell phone channel as previously described.
• Referring now toFIG. 20,vehicle800 may be provided withcommunication system801 includingaudio device34, shown powered by power system802 (e.g. battery, alternator, etc.) ofvehicle800.Audio device34 may be hardwired via wire(s)804 to transmitter/receiver806 including an IR transmitter (e.g. a light emitting diode (LED)) and an IR receiver (photoreceptor). As previously described,audio device34 can provide a plurality of channels of audio data. In other embodiments,audio device34 can provide other types of data, including video data, cellular telephone voice data, and text data. Thus, a video device such asDVD player803 may be connected toaudio device34, which in turn can encode the video signal from the DVD player as discussed previously and provide it to IR transmitter/receiver806 for transmission toward the rear ofvehicle800 via IR signals16.Vehicle800 may also include cellular telephone or otherwireless communication device805 that may be connected toaudio device34, which again can encode a voice stream from the telephone for IR transmission. As described below, equipment may be provided for two-way communication by passengers to converse on the telephone viaaudio device34 and other IR devices.
• System801 may further includeIR repeater810 that, similar to transmitter/receiver806, includes an IR transmitter and an IR receiver.Repeater810 receives IR signals16 and re-transmits them, increasing the effective transmission area ofsystem801.Repeater810 may be designed to relaysignals16 coming from the front ofvehicle800, from the rear, or from any other or all directions. Thus, depending upon the application,repeater810 may incorporate multiple receivers facing multiple directions of reception and multiple transmitters facing multiple directions of transmission.Repeater810 requires a power source (not shown) that may include a battery, a connection to the vehicle power supply, a solar panel installed on the roof ofvehicle800, or any other practicable or convenient power supply.
• System801 may optionally includecommunication subsystem820 includingadapter module822 powered via wire(s)823 connected to the power supply ofvehicle800, such as throughbrake light824. Transmitter/receiver826 is connected via wire(s)827 tomodule822 to receive IR signals16 and relay to the module, and to receive signals from module222 to transmit via IR toward other areas ofvehicle800.Module822 includes circuitry (including a DSP) similar toaudio device34 to accept data input and encode the data as described previously for IR transmission by transmitter/receiver826. The input data may be digital or analog, and thusmodule822 may include one or more ADCs to accept analog data and digitize it for encoding as disclosed herein.Subsystem820 may be preinstalled by the manufacturer ofvehicle800, thus allowing a subsequent purchaser of the vehicle to install custom IR devices as described below on an as-needed or as-required basis without the need of laborious, complicated additional wiring installation within the vehicle.
• Module822 may receive a wide variety of data, including analog or digital video data fromvideo camera830, for relay toaudio device34 via transmitter/receivers826,806, and optionally810. Audio device may include or be connected tovideo display831 for displaying the video data received fromvideo camera830.Video camera830 may be mounted at the rear of the vehicle to provide a real-time display of automobiles behindvehicle800 and acting essentially as a rear-view mirror and/or a proximity sensor to alert the driver if another vehicle or other obstacle is too close tovehicle800.Module822 may also accept audio input from an audio device such asmicrophone832.Microphone832 may be employed as an audio monitor, e.g. a baby monitor as described previously, or a medical monitor for an ill person travelling in the rear ofvehicle800. Microphone835 may also be used by aperson wearing headphones80 to access a cellular telephone device (or CB radio, or any other type of wireless communication device) connected toaudio device34, as previously discussed, to receive and conduct a conversation through the cellular telephone or other communication device. Thus,microphone832 may be physically separate from, or alternatively incorporated into,headphones80.Headphones80, or microphone835, may incorporate certain controls to access features of the cellular telephone or other communication device, such as hang-up, dial, volume control, and communication channel selection.
• Module822 may accept other data input, such as patient monitoring data (e.g. heartbeat, temperature, etc.) frommonitor833 that may be physically applied on a person travelling invehicle800 who may be in need of constant monitoring.Monitor833 may be any other type of monitor, and thus may be a temperature monitor for a container to be used to report the temperature of the container to the driver ofvehicle800, such as (for example) a food container being delivered by a food delivery service.
• System801 may further includevideo display device838 mounted, for example, in the back of a passenger seat for viewing by a passenger seated in a rearward seat (passengers are not shown inFIG. 20 for clarity).Display838 includesIR receiver839 for receiving IR signals16 containing, for instance, video data fromDVD player803, or fromvideo camera830.
• Optionally,game control device836 may also be connected tomodule822 for communicating withvideo gaming console837 connected toaudio device34. In this embodiment, passengers may wearheadphones80 to listen to the soundtrack of a game software executed byvideo gaming console837 to generate audio and video signals for transmission byaudio device34. The video signals may be displayed to the passengers ondisplay device838, and the passengers may interact with the game software being executed on the gaming console via inputs through game control device (e.g. a joystick, touch pad, mouse, etc.)836.
• Module822 may further output audio data toaudio speaker842, thereby eliminating the need to extend wires from the front to the rear ofvehicle800 for the speaker.Speaker842 may be powered by the vehicle power supply, in which case it may include an amplifier to amplify the audio signal received frommodule822. Alternatively,module822 may include all circuitry (including a DAC) necessary for processing received signals16 into an analog audio signal and amplifying the analog signal prior to providing it tospeaker842. The channel played throughspeaker842 may be selected through audio device34 (i.e. by the driver of vehicle800) or any other input device including game control device836 (i.e. by a passenger in the vehicle), and the channel thus selected may be indicated in the header of each packet transmitted from the audio device for decoding by a DSP withinmodule822.
• In other embodiments of the encoding schemes previously described (such as the scheme described in connection withFIG. 12), the data may be arranged in the transmit buffer(s) in various other configurations to reduce processing power consumption by the receiver. As one example, all data representing one channel may be stored in the buffer (and subsequently transmitted) sequentially, followed by the next channel and so forth. If a channel or channels are not available, those channels may be identified in the header of each packet. In this manner, the receiver DSP may power down during the time the inactive channel data is being received.
• When one or more channels are inactive, the transmitter may increase the bandwidth allocated to each channel, e.g. by sampling the incoming audio data at a higher rate to provide a higher-quality digital stream. Alternatively, the transmitter may take advantage of excess capacity by increasing error detection and/or correction features, such as including redundant samples or advanced error correction information such as Reed-Salomon values.
• To minimize reception errors, the number of audio samples included in each packet may also be adjusted depending on the number and type of errors experienced by the receiver. This feature would likely require some feedback from the receiver on the errors experienced, based upon which the transmitter DSP may be programmed to include fewer audio samples per packet.
• Other error detection schemes may also be employed. As one example, a code may be randomly changed from packet to packet, and inserted not only in the header but also at a location or locations within the data block. Alternatively, the same encoded value may be used. The location(s) of the value(s) may also be randomly changed from packet to packet to remove the effects of fixed frequency errors. The location(s) may be specified in the header of each packet, and the DSP programmed to read the value then check for the same value at the specified location(s) within the data block. If the value(s) at these location(s) do not match the value specified in the header, the DSP may discard the packet as containing errors and optionally mute the output as described previously.
• To conserve bandwidth and enhance processing efficiency, the encoded value(s) may contain additional information, i.e. instead of a random value the encoded value may be representative of, for example, the active and inactive channels. The encoded value would preferably be placed at least in one location of the data block assigned to each active channel to ensure that the value is in the channel selected by the listener for processing by the DSP. In another embodiment, multiple encoded values may be used, each representative of a different system variable or other information (e.g. one encoded value indicative of active channels, another containing a check-sum value, another containing a Reed-Salomon value for forward error-correction, etc.).
• In a bi-directional system such assystem801,headphones80 may include an IR transmitter to enable the receiver DSP to transmit reception error values toaudio device34 related to the received data. Based upon these values, the transmitter DSP may undertake certain error correction actions, including retransmission of bad data packets, adjustment of data packet size (e.g. transmit packets containing less data when the error rate is above a predetermined threshold, or adjust the amount of data per packet dynamically as a function of the reception error rate), and increase of transmission power generated byIR transmitter18.
• Referring now toFIG. 21, in analternative embodiment vehicle900 includescommunication system901. As discussed in connection with other embodiments,communication system901 may includeaudio device34 hardwired through wire(s)804 to photo transmitter/receiver806.Communication system901 may also includeIR transmitter section18 to receive encoded data fromaudio device34 and to control and power photo transmitter/receiver806 to emit a digital bit stream of optical pulses.IR transmitter section18 may be provided separately fromaudio device34 as shown inFIG. 18, for ease of installation, repair, maintenance, and upgrade, or may alternatively be included withinaudio device34.
• Audio device34 may provide a plurality of channels of audio and other data, and is shown as receiving audio and video data fromDVD player803, audio and/or video data from auxiliary audio device922 (e.g. MP3 player, digital satellite radio tuner, video game player, etc.) andcellular telephone805, geographical location data fromGPS unit920, and various vehicle data (e.g. telemetry information) from a vehicle central processing unit (CPU)924 that monitors and controls various functions ofvehicle900. As previously described,communication system901 may provide for two-way communications, andaudio device34 may thus also accept data received by transmitter/receiver806 from other IR devices invehicle900 and channel the data to such devices asvehicle CPU924 andcellular telephone805.CPU924 may receive information such as proximity information from video camera/proximity sensor830 to display an appropriate video picture or a warning to the driver ofvehicle900.
• With continued reference toFIG. 21,communication system901 may further includecommunication subsystem921 including IR receiver/transmitter926 hardwired via wire(s)827 tocommunication module923 that, as described elsewhere with connection to module822 (FIG. 17), may be hardwired to video camera/proximity sensor830 to receive data from the video camera and transmit it tovehicle CPU924 through IR receiver/transmitters926,806 andaudio device34.Module923 may also receive audio data fromaudio device34 and provide the audio data to subwoofer942 that may be installed in the trunk or, as shown, underneath the rear seat ofvehicle900. Additionally,module923 may also be hardwired to trunk-mountedCD changer950 and accept audio data from the CD changer to transmit toaudio device34 for playback withinvehicle900, as well as receive control commands input by the vehicle driver throughaudio device34 to control the CD changer, such as CD and track selection, shuffle, repeat, etc.
• Module923 may include one or more DACs to decode audio data received fromaudio device34 as described elsewhere and convert the decoded data to analog form forsubwoofer942. Alternatively,subwoofer942 may include a DAC and thus be able to accept decoded digital audio data directly frommodule923.Module923 may also include one or more ADCs to accept analog data fromvideo camera830 andCD changer950, convert it to digital form, encode it as described elsewhere herein, and transmit it toaudio device34.Vehicle CPU924 may be connected tocommunication system901 to relay telemetry and information related to the vehicle to the CPU. For example, tire pressure monitor952 may be disposed in the rear area ofvehicle900 and may be hardwired tomodule923 to transmit information related to the rear tire(s) pressure tovehicle CPU924. In this manner, the usefulness ofcommunication system901 may be extended beyond entertainment functions to vehicle operational functions. In a further embodiment, IR receiver/transmitter926 may incorporate a repeater to receive IR signals from any IR transmitters invehicle900, amplify the received IR signals, and re-transmit the received signals for reception by other IR receivers in the vehicle.
• Wireless speaker940 may be mounted in a door ofvehicle900 or at any other practicable location, and includes IR receiver/transmitter941. Preferably speaker940 includes a DSP to decode encoded digital audio data received from IR receiver/transmitters806,926 and a DAC to convert the decoded audio data to analog form for playback withinvehicle900. Both speaker940 andsubwoofer942 require a power source, which may be provided by thevehicle900 power supply such as from the power supply to the rear lights of the vehicle.
• Still referring toFIG. 21, two-way headphones980 include IR receiver/transmitter982 andmicrophone984. IR receiver/transmitter982 communicates via an optical bit stream of data withaudio device34 through IR receiver/transmitter806 or, optionally, through IR receiver/transmitter926 that includes a repeater as described previously. Two-way headphones980 may be used to accesscellular telephone805 throughaudio device34 to place a call and conduct a two-way conversation. Two-way headphones980 may include a numeric pad for dialing, or alternativelyaudio device34 may include voice recognition capabilities to allow user933 (using headphones980) to simply select a predetermined channel for placing telephone calls and then activate and operatecellular telephone805 by speaking commands intomicrophone984. Two-way headphones980 may further include an ADC connected tomicrophone984 to digitize the voice ofuser933 for encoding and IR transmission as described elsewhere herein. Two-way headphones980 preferably also provide the other functions provided byheadphones80 as previously described, including controlling audio volume and selecting one of a plurality of communication channels.
• With continued reference toFIG. 21,remote controller936 includes IR receiver/transmitter984 for two-way communication withaudio device34 via IR receiver/transmitter806 and, optionally, a repeater included in IR receiver/transmitter926.Remote controller936 may provide any one or more of a plurality of controls, including but not limited to key pads, joysticks, push buttons, toggles switches, and voice command controls, and may further provide sensory feedback such as audio or tactile/vibrations.Remote controller936 may be used for a variety of purposes, including accessing and controllingcellular telephone805 as previously described.Remote controller936 may also be used to access and control video game player922 to play a video game displayed on video display(s)838, with the game audio track played throughheadphones80,980.Remote controller936 may further be used to controlvideo display838 and adjust display functions and controls, to controlDVD player803 to display a movie onvideo display838 and control its functions (e.g. pause, stop, fast forward), to control trunk-mountedCD changer950, to request telemetry data fromvehicle CPU924 to display onvideo display838, or to controlother vehicle900 functions such as locking/unlocking doors and opening/closing windows. Two or moreremote controllers936 may be provided invehicle900 to allow two ormore users933,935 to play a video game, displayed individually on multiple, respective video displays838. Eachremote controller936 may accessaudio device34 and video game player922 through a separate communication channel and thus enable the game player to provide different, individual video and audio streams to eachrespective user933,935 through therespective video displays838 andheadphones980,80.Headphones80,980 may further be programmed to receive an IR signal fromremote controller936 to select another channel, or to automatically select the appropriate channel based upon the function selected by the user (e.g. play a video game, watch a DVD).
• DSP76 ofheadphones80 may be programmed to identify differentaudio devices34, such as may be found in a vehicle and in a home. Eachaudio device34 may thus include further information in the header of each data packet to provide a unique identifier.DSP76 may further include programmable memory to store various user-selectable options related to eachaudio device34 from which the user ofheadphones80 may wish to receive audio and other data. Thus, by way of example,DSP76 may be programmed to receive and decode a predetermined number of stereo and/or mono audio channels when receiving data from a vehicle-mountedaudio device34, and to receive and decode six channels of mono audio data to provide a true 5.1 audio experience when receiving data from anaudio device34 connected to a home theatre system.
• In another embodiment,headphones80 may be provided with user customizable features, such as tone controls (e.g. bass, treble) that may be adjusted to different values for each available channel, and which are automatically detected and applied when the respective channel is selected by the user. Additionally, custom features may also be set for individualaudio devices34, such an in-vehicle audio device and an in-home audio device as described above.Headphones80 may therefore be provided with additional controls such as bass and treble controls, and other signal processing options (e.g. panorama, concert hall, etc.). Custom settings may be retained as a headphone profile in a memory included withinheadphones80, which may be any type of erasable memory. Alternatively, for two-way headphones980, custom feature values adjusted by the user may be transmitted toaudio device34 for storing in a memory within the audio device, and these custom values may then be embedded in the data stream representing each channel (e.g. in the header of data packets) to be recovered byheadset980 and applied to the signal of the selected channel.
• Alternatively, custom features may be adjusted viaaudio device34 so that even one-way headphones80 may enjoy customized settings. In embodiments wherein customized features are stored in memory byaudio device34, each individual set ofheadphones80 and/or980 may be provided with a means of individual identification, which may be entered by a user via the controls provided on the headphones (e.g. define the headphones as number one, two, three, etc.). The individual identification will allow the audio device to embed the custom settings for every set of headphones in the data stream representing each channel to be recovered by each set of headphones, following which each set of headphones will identify and select its own appropriate set of custom settings to apply to the signal of the channel selected by the user of the particular set of headphones.
• In addition to custom headset profiles, users may be allowed to specify individual user profiles that specify the particular setting preferences of each individual user of headphones withinvehicle900. Such individual profiles may be stored inaudio device34 and transmitted within the data stream as described above. In this embodiment, each user may be required to input a unique identifier through the controls of the selectedheadphones80 to identify herself to the headphones, which may be programmed to then extract the individual user profile of the user wearing the headphones and applying the custom settings in the profile to the signal of the user selected channel. Such profiles may be embedded in each data packet, or may be transmitted only once whenaudio device34 is first powered on, or alternatively may be transmitted at regular intervals. Alternatively, all user profiles may be stored in a memory by each set ofheadphones80 within avehicle900, and the profiles may updated intermittently or every time upon power on ofaudio device34.
• With reference now toFIG. 22, communication system is provided invehicle988, wherein the vehicle includesdata bus990.Data bus990 is connected tovehicle CPU924 and extends throughoutvehicle988 to connect various devices (e.g. video camera830, CD changer950) within the vehicle to the CPU.Data bus990 may extend through the headliner ofvehicle988, as shown, or may take alternative paths through the vehicle to connected the desired devices. Data bus may be a fiber optic bus or may be an electronic wired bus, and may operate at various transmission speeds and bandwidths. In one embodiment,data bus990 may operate according to the Bluetooth wireless communications standard, or to the Media Oriented Systems Transport (MOST) communications standard for fiber optic networks.
• Communication system991 includesIR modules992 mounted at one or more locations withinvehicle988 and connected todata bus990. EachIR module992 may contain an IR receiver (photoreceptor) and may additionally contain an IR transmitter (e.g. one or more LEDs). As previously described, a repeater may also be incorporated into eachIR module992 to re-transmit received IR signals. Additionally, eachIR module992 includes circuitry (e.g. network interface card) for interfacing withdata bus990 to read data being transmitted over the bus and convert the data to IR signals for transmission by the LED(s), and also to convert received IR signals to a data format accepted by the bus and transmit such data over the bus toaudio device34 or to any other devices connected to the bus. The interface circuitry may further include a buffer or cache to buffer data if the IR receiver and/or transmitter operate at a different speed fromdata bus990.
• In this embodiment,audio device34 is not required to be the central control unit ofcommunication system991, which instead can be a distributed system wherein theIR modules992 enable any IR device insidevehicle988 to interface with any other IR device operating with a compatible coding scheme or with any other device that is connected todata bus990. By properly addressing and identifying the data transmitted over data bus990 (e.g. via information placed in the header of each data block or data packet), each device connected to the data bus can identify the channel of data it is required to decode and use, and may optionally be assigned a unique address to which the data it is intended to receive can be uniquely addressed, This hybrid network is easily expandable as no additional wiring is needed to connect additional devices to the network; instead, each new device can be equipped with an IR transmitter/receiver that allows the device to connect to the network through one of the wireless interfaces.
• With reference now toFIG. 23, in yet another embodiment,communication system1000 is provided in building1010 wherein the building includescommunication network1020.Network1020 may be a Local Area Network (LAN) that may be wired or may be wireless, such as an 802.11 (WiFi) compliant wireless (RF) network. Alternatively,network1020 may simply be a wired data pipeline connected, for example, to local cabletelevision company network1022. As known in the art,network1020 may thus interface withcable network1022 to receive media content such as television and music channels, and further to provide a connection to the Internet viacable modem1024.
• Network1020 includes wireless (radio)RF transceiver1030 hardwired to the network and installed inroom1011 of building1010 to broadcast the data flowing on the network throughout the building via RF signals1032. To minimize RF interference throughout building1010 from multiple RF transmitters,room1012 in the building may be equipped with interface encoder/decoder1040 connected toRF antenna1034 to receiveRF signals1032 fromRF transmitter1030 carrying data fromnetwork1020. Encoder/decoder1040 may then encode the received network signals as described elsewhere herein, e.g. in connection with the discussion ofFIG. 10, and drive an IR LED of IR transmitter/receiver1050 to emitIR signal1052 carrying the network data. Devices in the room such as aPC1060 may be equipped with IR transmitter/receiver1070 to receiveIR signal1052 and encoder/decoder1080 extract the data from the IR signal, as well as to encode data from the PC and transmit it asIR signal1062 to be received by interface encoder/decoder1040 through transmitter/receiver1050. Interface encoder/decoder1040 may then decode or de-multiplex data carried byIR signal1062 fromPC1060 and pass it on toRF antenna1034, which in turn transmits the data as RF signals1036 to be received bytransceiver1030 and communicated tonetwork1020.
• With continued reference toFIG. 23,room1013 of building1010 may be equipped withhome theatre system1100 connected to network1020 to receive television and audio programming. The home theatre system may also be connected todecoder1110 to receive one or more channels of audio from a pre-amp of the home theatre system and driveIR transmitter1120 to transmit the channels of audio as IR signals1122, as described elsewhere herein. Devices inroom1012 such aswireless headphones14 andremote speakers1130 may each be equipped withIR receivers70 and decoder circuitry for decoding IR signals1122, as previously described. IR signals1122 may carry audio information such as5 channels of monaural audio for eachspeaker1130 forming a so-called 5.1 audio system. IR signals may also carry multiple channels of audio such thatlistener1150 wearingheadphones14 may choose to listen to a different audio channel than the channel being played byloudspeakers1130. It must be understood that many other types of devices may be connected wirelessly tonetwork1020 including, but not limited to, telephones, facsimile machines, televisions, radios, video game consoles, personal digital assistants, various household appliances equipped for remote control, and home security systems.
• Hybrid system1000 thus utilizes the ability of RF signals to propagate through walls, but minimizes the RF interference that may arise in such situations.System1000 is also highly flexible and allows connecting multiple additional devices, such asPC1060, to a wired network such asnetwork1020 without actually installing any additional cable or wiring in the building. Instead, a single interface encoder/decoder1040 needs to be installed in each room of the building and devices in any of the rooms so equipped can then be connected tonetwork1020 through either a one-way decoder such asdecoder1110 or a two-way encoder/decoder such as encoder/decoder1080. In this manner, older buildings can be easily and cost-effectively retrofitted to building modern offices with the requisite network/communication capabilities.
• With reference now toFIG. 24,n vehicle800 may be equipped with a communication system as previously described, includingaudio device34 hardwired to IR receiver/transmitters806. In this embodiment the communication system includes two IR receiver/transmitters806L and806R, each individually hardwired toaudio device34 viawires807L and807R, respectively, to receive digital signals therefrom as previously described elsewhere herein. The IR receiver/transmitters806L and806R are mounted substantially above the left and right rear seat, respectively, ofvehicle800 to emit relatively narrowly focused IR signals16L,16R respectively for individual receipt byheadset receiver units14 worn by passengers seated in the left and right rear seats ofvehicle800, respectively (labeled inFIG. 24 as14L,14R for convenience of discussion). In this manner, each headset14L,14R may receive an individual signal16L,16R respectively. Signals16L,16R may be identical to one other, or may be different from one another. Thus, the present embodiment allows further differentiation amongst a plurality of headsets and other wireless devices equipped as described previously to receive and/or transmit wireless signals such as signals16L,16R.
• Signals16L,16R may be unidirectional or, as shown, may be bidirectional when the wireless devices are equipped with wireless receivers as well as transmitters. In this embodiment, simpler, more cost-effective wireless devices may be provided that will allow each headset (or other wireless device) user to communicate individually with theaudio device34. In this manner,audio device34 may be configured to provide multiple, individual wireless (e.g. IR) signals, each carrying a plurality (e.g. four) of multiplexed channels of data such as audio and/or video data, and therefore provide even more choices to wireless device users. The individual wireless signal (e.g. IR signals16L,16R, etc.) that is transmitted by each receiver/transmitter (e.g. IR receiver/transmitters806L,806R, etc.) may be selected via theaudio device34, and/or alternatively by the user of each two-way wireless device capable of transmitting a wireless device to its respective IR receiver/transmitter.
• To achieve the desired narrow focus of the wireless signals, in an embodiment where the wireless signals areIR signals16, IR LEDs may be provided in the IR receiver/transmitters that are aimed directly below and towards the rear seats ofvehicle800. As further described below, it may be advantageous to use LEDs having relatively small physical dimensions, such as SMD (Surface Mount Device) LEDs that can be as small as 800 μm wide and 1,000 μm tall. It will be appreciated that such embodiments simplify overall design and also minimize cross interference between different signals due to the narrow focus of the LEDs.
• Alternately, serially encodeddigital bitstream16 may be further multiplexed, for example at higher speeds, so that a significantly greater number of selectable channels may be made available for each user, for example for use on an airplane.
• Although the above embodiments have been described with reference to a system transmitting digital signals, it must be understood that the embodiments described herein are equally applicable to an analog system that transmits analog signals. Thus, the embodiments described herein may be used to offer users of analog wireless devices such as headsets access to multiple channels by selecting the signal to be transmitted by their respective wireless receiver/transmitter. Thus, this embodiment may obviate the need for multiplexing multiple channels of data into a single signal altogether (for both analog and digital systems), as a user of a wireless device such as a headset may select an individual channel of data (such as stereo audio), separate and different from a channel of data received by another user in the same vehicle, to be transmitted by the respective wireless receiver/transmitter located above the user.
• The embodiments described herein may also be used to provide a mix of analog and digital signals. In this manner, a vehicle may be equipped or retrofitted with one or more analog wireless receiver/transmitters to transmit data channels from an audio device such asaudio device34 for receipt by analog wireless devices, and may also be provided with one or more digital wireless receiver/transmitters to transmit digitized data channels form the same or an additional audio (or video, or other) device for receipt by digital wireless devices. A vehicle so equipped may allow user a wider variety of options for wireless devices to use therein.
• In one embodiment as described herein and illustrated inFIG. 25, IR receiver/transmitter806 (only one shown for clarity) is mounted within, that is behind the visible surface of, theheadliner809 ofvehicle800. As is known, the headliners of vehicles extend below, and are attached to, the roof of the vehicle. The headliners are typically formed of apliable material811 such as polystyrene foam or other foam and covered with a sheet of an estheticallypleasing material813 such as cloth or fabric or PVC. In one possible embodiment, a hollow space815 may be formed withinheadliner809 to snugly receive an IR receiver/transmitter806 therein. Anelongated space817 may also be formed within the headliner and extending from hollow space815 to acceptwire807 therein and conduct the wire towards the front of the vehicle, whereaudio device34 will typically be located.Headline cover813 may be advantageously formed of a material that is transparent to the wireless signals emitted by the receiver/transmitter (e.g. the IR signals emitted by IR receiver/transmitter806). Alternatively, an opening may be formed incover813 to allow the wireless signals to pass therethrough, and optionally a secondtransparent cover819 may be installed within the opening and over the wireless receiver/transmitter for protective and/or esthetic reasons.
• Referring now toFIG. 26,communication system1140 may includecomputer1142, or other desktop or portable unit, on which is mountedtransmitter18, connected thereto bycable1148 which may plug into a serial or USB or other conventional port.Transmitter18 transmits serially encodeddigital bitstream16 toheadphones14 or computer speakers such asspeakers1144 and1146, each of which may have appropriate decoders and optionally, a switching selector, as shown for example inFIG. 1.
• Communication system1140 provides computer generated audio output fromcomputer1142 to a listener who may selectably usespeakers1144 and1146 orheadphones14.Transmitter18 receives one or more channels of digitally formatted audio viacable1148 fromcomputer1142 or, for compatibility with some computer systems,transmitter18 may receive one or more channels of audio formatted audio viacable1148 and convert the audio to digital signals with a DAC or similar device as described above herein.Transmitter18 generates serially encodeddigital bitstream16 for simultaneous reception byspeakers1144,1146 andheadset14.
• Volume adjustment andcontrol knob1152 represents manual adjustments that may be made via computer by data entry represented byknob1152 or via aphysical knob1152 as shown, and/or byknob1152 positioned onheadphones14 or one or more of thecomputer speakers1144,1146. One of the control inputs to be made viaknob1152 may be the selection of which sound producing device,computer speakers1144,1146 orheadphones14, should be active at any time. It is typically desirable tomute computer speakers1144,1146 while receiving audio viaheadphones14 in order to minimize ambient noise in the vicinity ofcomputer1142. Similarly, because headphones are typically battery powered, it is desirable to mute and or turn off power toheadphones14 when not in use. In addition, becausecomputer speakers1144,1146 are not connected by cable tocomputer1142, it may be convenient to provide them with battery power in order to avoid the necessity of provided electric power to them via a transformer connected to a standard AC power outlet.
• It may be most convenient to select headphones or speakers via data entry orknob1152 oncomputer1142. The selection may be implemented by techniques described above such as the use of codes positioned within serially encodeddigital bitstream16. Referring now also toFIG. 12, upon selection ofspeakers1144,1146, a code word such as “SPKRS” may be inserted at a known location withinheader87 to indicate that selection. The receiver unit withinheadphones14 may be programmed to mute sound reproduction unless a code word such as “HDFNS” is found at the known location whilespeakers1144,1146 maybe programmed to mute if the SPKRS is not found at that location.
• In a preferred embodiment, two copies of the code word may be position within serially encodeddigital bitstream16 for comparison. As disclosed above, by detecting and comparing codes at two locations, error events can be detected and monitored. After a particular quantity of error events have been detected and monitored within a limited time frame, the muting function may operate until, and if, no error events are detected and monitored for a set time period.
• The auto-off function disclosed above may also be used to causeheadphones14 and/orspeakers1144,1146 to disconnect their battery power when no sounds have been reproduced for a particular time period. The auto-off function may be combined with the error event function so that a particular number of monitored error events in a certain period or a length of the muting period may cause the sound reproducing unit to disconnect itself from battery power. A similar operation can also be used to provide a disconnect from electrical power from an AC wall outlet applied, for example, tospeakers1144,1146.
• Referring now again toFIG. 26, signalinput connector1150 may serve to apply priority signals tocomputer1142, such as indications of a landline, cell phone or doorbell ringing or a driveway or yard sensor output, that may be applied to serially codeddigital bitstream16 for reproduction onheadphones14 and/orcomputer speakers1144,1146. This feature is similar to the priority channel discussed above with respect toFIG. 19. The data applied to serially codeddigital bitstream16 may simply be a tone or beep indicating one of the signals applied to signalinput connector1150. The data may also represent preprogrammed messages, such as “The phone is ringing” or may represent audio received for example from a baby room monitor. The reproduced data may be superimposed on the current audio be reproduced byheadphones14 orspeakers1144,1146 or may be on a separate priority automatically selected when such data is received.
• Knob1152 may also be used for volume control performed at a central location. For example, when the selected code in serially encodeddigital bitstream16 is changed from SPKRS to HDFNS, the volume of the audio reproduced byheadphones14 may not be appropriate even though it was the volume of the audio reproduced byspeakers1144,1146. One ormore knobs1152 may also, or alternately, be positioned oncomputer1152,transmitter18 and of one or both ofspeakers1144,1146.
• Referring now toFIG. 27 and any of the communication system embodiments disclosed herein such asFIG. 1, one or more of the sources of audio data such asMP3 player44, or a digital camera or other data source, may be a portable device such a portable MP3 player45 connectable wireless by a bitstream, similar tobitstream16, to a suitable receiver such asaudio device34 connected tomaster controller26 for transmission viabitstream16 toheadphones14.
• In particular,communication system1154 may be a bidirectional data system in whichdigital bitstream17 from portable MP3 player45 is received by combined transmitter/receiver19 which also transmitsbitstream16 toheadphones14.Bitstream17 may then be applied toaudio device34 and used to provide one or more audio channels inbitstream16 selectable for reception byheadphones14 or suitable speakers. In this embodiment, remote MP3 player45 may be used within the environment ofcommunication system1154 to provide one of the audio channels onheadset14.
• Alternatively,transmitter18 on portable MP3 player45 may be configured to providebitstream17 in a form received and decoded directly byheadset14. In this embodiment, portable MP3 player45 may be used to provide audio in the environment ofsystem1154 without operation ofaudio device34 or transmitter/receiver19, for example, in a vehicle when the motor has been turned off. In this embodiment, portable MP3 player45 can be used with any of theheadsets14 fromcommunication system1140 without the rest of the system.
• In a further alternative, both configurations can be combined so that portable MP3 player45 can be selectively used to directly provide audio toheadphones14, or provide audio via a channel included withinbitstream16. In this configuration, a further alternative may be provided in whichbitstream17 is decodable and reproducible only viaheadset15 which need not beresponsive bitstream16. This configuration may be desirable to provide the opportunity for the use ofheadset15 for private listening whether withinsystem1154 or elsewhere. In one variation, this configuration may not provide abitstream17 suitable for direct reception byheadphones14, reducing the likelihood thatheadphones14 may be removed from the environment ofsystem1154 for use elsewhere.
• In a further embodiment,bitstream17 may be recorded in a memory or hard disk associated withaudio device34 for later play.
• Having now described the inventions in accordance with the requirements of the patent statutes, those skilled in this art will understand how to make changes and modifications to the inventions disclosed herein to meet their specific requirements or conditions. Such changes and modifications may be made without departing from the scope and spirit of the disclosed inventions.

Claims (21)

1-11. (canceled)

12. A wireless audio distribution system, comprising:

a wireless transmitter, responsive to a plurality of audio input channels, for transmitting an encoded digital bitstream serially combining each of the audio input channels with control data;

a receiver responsive to the transmitted encoded digital bitstream for decoding a preselected one of the plurality of the audio input channels from the digital bitstream for reproduction; and

at least one speaker for reproducing the preselected audio input channel in accordance with the control data.

13. The invention ofclaim 12 wherein the wireless transmitter further comprises:

a selector for selecting the preselected audio channel for reproduction by the at least one speaker.

14. The invention ofclaim 12, wherein the receiver further comprises:

a control unit responsive to at least portions of the control data for controlling the reproduction of the preselected audio channel by the speaker in accordance with the at least portions of the control data.

15. The invention ofclaim 14, wherein the control unit decodes the preselected audio input channel from the digital bitstream in accordance with the at least portions of the control data.

16. The invention ofclaim 15, further comprising:

an input device for inputting the selection of one of the plurality of audio input channels to be the preselected audio channel.

17. The invention ofclaim 15 wherein the wireless transmitter is responsive to the selection of the one of the plurality of audio input channels to be the preselected channel.

18. The invention ofclaim 15 wherein the receiver is responsive to the selection of the audio input channel to be the preselected channel.

19. The invention ofclaim 15 wherein the digital bitstream data includes the selection of the audio input channel to be the preselected channel.

20. The invention ofclaim 15 further comprising:

at least one additional receiver; and

at least one speaker associated with the at least one additional receiver, wherein the at least one additional receiver is responsive to the transmitted encoded digital bitstream for decoding a second preselected audio input channel from the digital bitstream and the at least one additional speaker associated with the at least one additional receiver reproduces the second preselected audio input channel.

21. The invention ofclaim 20 wherein the at least one additional speaker receiver and at least one speaker associated therewith further comprises:

a plurality of pairs of additional receivers and speakers, each such pair reproducing an audio channel representing music as heard by a listener from different directions including from the front and rear of the listener.

22. The invention ofclaim 12, further comprising:

a pair of wireless headphone responsive for reproducing the preselected audio channel in accordance with the control data.

23. The invention ofclaim 22, further comprising:

a selector switch for selecting either the speaker or the headphones to reproduce the preselected audio input channel.

24. The invention ofclaim 23 wherein the selector switch causes a modification of the control data to selectively cause the speaker or the headphones to reproduce the preselected audio input channel.

25. The invention ofclaim 23 wherein the receiver further comprises:

an error detection circuit for comparing portions of the control data to detect errors; and

an off circuit for turning off the selected speaker or headphone if the detected errors exceed a predetermined threshold.

26. The invention ofclaim 25 further comprising:

an error correction circuit for correcting the detected errors.

27. A wireless speaker system comprising:

a receiver, responsive to a wirelessly transmitted, encoded digital bitstream serially combining each of a plurality of the audio input channels with control data disbursed therein, for decoding a preselected one of said audio input channels; and

a speaker system responsive to the receiver for reproducing the decoded, preselected audio input channel.

28. The wireless speaker system claimed inclaim 27, further comprising:

a control unit responsive to at least portions of the control data for controlling the reproduction of the preselected audio channel by the speaker in accordance with the control data.

29. The wireless speaker system claimed inclaim 28 wherein the preselected audio input channel is selected by the control data.

30. The wireless speaker system claimed inclaim 28 wherein the preselected audio input channel is selected by the receiver.

31. The wireless speaker system claimed inclaim 28 wherein the preselected audio input channel is selected by the speaker.

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